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  <title>Object - Knowledge</title>
  <meta name="keywords" content="Object,html css node vue node">
  <meta desc name="description" content="html css node vue node - weijt - Knowledge">
  
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<meta property="og:title" content="Object">
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<meta property="og:description" content="Object.is()1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253&#x2F;&#x2F; ES5判断两个值是否相等，有两种方法：相等运算符（&#x3D;&#x3D;）和严格相等运算符（&#x3D;&#x3D;&#x3D;）。&#x2F;&#x2F; 这两种方法都有缺点，前者会自动转换数据类型，后者判断NaN不等于自身，+0 等于 -0&#x2F;">
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  <style>
    /* 首屏样式 */
    #safearea {
  display: none;
}
:root {
  --color-site-body: #f4f4f4;
  --color-site-bg: #f4f4f4;
  --color-site-inner: #fff;
  --color-site-footer: #666;
  --color-card: #fff;
  --color-text: #444;
  --color-block: #f6f6f6;
  --color-inlinecode: #c74f00;
  --color-codeblock: #fff7ea;
  --color-h1: #3a3a3a;
  --color-h2: #3a3a3a;
  --color-h3: #333;
  --color-h4: #444;
  --color-h5: #555;
  --color-h6: #666;
  --color-p: #444;
  --color-list: #666;
  --color-list-hl: #30ad91;
  --color-meta: #888;
  --color-read-bkg: #e0d8c8;
  --color-read-post: #f8f1e2;
  --color-copyright-bkg: #f5f5f5;
}
* {
  box-sizing: border-box;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  outline: none;
  margin: 0;
  padding: 0;
}
*::-webkit-scrollbar {
  height: 4px;
  width: 4px;
}
*::-webkit-scrollbar-track-piece {
  background: transparent;
}
*::-webkit-scrollbar-thumb {
  background: #3dd9b6;
  cursor: pointer;
  border-radius: 2px;
  -webkit-border-radius: 2px;
}
*::-webkit-scrollbar-thumb:hover {
  background: #ff5722;
}
html {
  color: var(--color-text);
  width: 100%;
  height: 100%;
  font-family: UbuntuMono, "Varela Round", "PingFang SC", "Microsoft YaHei", Helvetica, Arial, Menlo, Monaco, monospace, sans-serif;
  font-size: 16px;
}
html >::-webkit-scrollbar {
  height: 4px;
  width: 4px;
}
html >::-webkit-scrollbar-track-piece {
  background: transparent;
}
html >::-webkit-scrollbar-thumb {
  background: #54b5a0 linear-gradient(45deg, rgba(255,255,255,0.4) 25%, transparent 25%, transparent 50%, rgba(255,255,255,0.4) 50%, rgba(255,255,255,0.4) 75%, transparent 75%, transparent);
  cursor: pointer;
  border-radius: 2px;
  -webkit-border-radius: 2px;
}
html >::-webkit-scrollbar-thumb:hover {
  background: #54b5a0 linear-gradient(45deg, rgba(255,255,255,0.4) 25%, transparent 25%, transparent 50%, rgba(255,255,255,0.4) 50%, rgba(255,255,255,0.4) 75%, transparent 75%, transparent);
}
body {
  background-color: var(--color-site-body);
  text-rendering: optimizelegibility;
  -webkit-tap-highlight-color: rgba(0,0,0,0);
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
  -ms-text-size-adjust: 100%;
}
body.modal-active {
  overflow: hidden;
}
@media screen and (max-width: 680px) {
  body.modal-active {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
  }
}
a {
  color: #2092ec;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
a:hover {
  color: #ff5722;
}
a:active,
a:hover {
  outline: 0;
}
ul,
ol {
  padding-left: 0;
}
ul li,
ol li {
  list-style: none;
}
header {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
}
img {
  border: 0;
  background: none;
  max-width: 100%;
}
svg:not(:root) {
  overflow: hidden;
}
hr {
  -moz-box-sizing: content-box;
  box-sizing: content-box;
  -webkit-box-sizing: content-box;
  -moz-box-sizing: content-box;
  height: 0;
  border: 0;
  border-radius: 1px;
  -webkit-border-radius: 1px;
  border-bottom: 1px solid rgba(68,68,68,0.1);
}
button,
input {
  color: inherit;
  font: inherit;
  margin: 0;
}
button {
  overflow: visible;
  text-transform: none;
  -webkit-appearance: button;
  cursor: pointer;
}
@supports (backdrop-filter: blur(20px)) {
  .blur {
    background: rgba(255,255,255,0.9) !important;
    backdrop-filter: saturate(200%) blur(20px);
  }
}
.shadow {
  box-shadow: 0 1px 2px 0px rgba(0,0,0,0.1);
  -webkit-box-shadow: 0 1px 2px 0px rgba(0,0,0,0.1);
}
.shadow.floatable {
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
.shadow.floatable:hover {
  box-shadow: 0 2px 4px 0px rgba(0,0,0,0.1), 0 4px 8px 0px rgba(0,0,0,0.1), 0 8px 16px 0px rgba(0,0,0,0.1);
  -webkit-box-shadow: 0 2px 4px 0px rgba(0,0,0,0.1), 0 4px 8px 0px rgba(0,0,0,0.1), 0 8px 16px 0px rgba(0,0,0,0.1);
}
#l_cover {
  min-height: 64px;
}
.cover-wrapper {
  top: 0;
  left: 0;
  max-width: 100%;
  height: 100vh;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  flex-wrap: nowrap;
  -webkit-flex-wrap: nowrap;
  -khtml-flex-wrap: nowrap;
  -moz-flex-wrap: nowrap;
  -o-flex-wrap: nowrap;
  -ms-flex-wrap: nowrap;
  -webkit-box-direction: normal;
  -moz-box-direction: normal;
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
  -webkit-flex-direction: column;
  -ms-flex-direction: column;
  flex-direction: column;
  align-items: center;
  align-self: center;
  align-content: center;
  color: var(--color-site-inner);
  padding: 0 16px;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  position: relative;
  overflow: hidden;
  margin-bottom: -100px;
}
.cover-wrapper .cover-bg {
  position: absolute;
  width: 100%;
  height: 100%;
  background-position: center;
  background-size: cover;
  -webkit-background-size: cover;
  -moz-background-size: cover;
}
.cover-wrapper .cover-bg.lazyload:not(.loaded) {
  opacity: 0;
  -webkit-opacity: 0;
  -moz-opacity: 0;
}
.cover-wrapper .cover-bg.lazyload.loaded {
  animation-delay: 0s;
  animation-duration: 0.5s;
  animation-fill-mode: forwards;
  animation-timing-function: ease-out;
  animation-name: fadeIn;
}
@-moz-keyframes fadeIn {
  0% {
    opacity: 0;
    -webkit-opacity: 0;
    -moz-opacity: 0;
    filter: blur(12px);
    transform: scale(1.02);
    -webkit-transform: scale(1.02);
    -khtml-transform: scale(1.02);
    -moz-transform: scale(1.02);
    -o-transform: scale(1.02);
    -ms-transform: scale(1.02);
  }
  100% {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@-webkit-keyframes fadeIn {
  0% {
    opacity: 0;
    -webkit-opacity: 0;
    -moz-opacity: 0;
    filter: blur(12px);
    transform: scale(1.02);
    -webkit-transform: scale(1.02);
    -khtml-transform: scale(1.02);
    -moz-transform: scale(1.02);
    -o-transform: scale(1.02);
    -ms-transform: scale(1.02);
  }
  100% {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@-o-keyframes fadeIn {
  0% {
    opacity: 0;
    -webkit-opacity: 0;
    -moz-opacity: 0;
    filter: blur(12px);
    transform: scale(1.02);
    -webkit-transform: scale(1.02);
    -khtml-transform: scale(1.02);
    -moz-transform: scale(1.02);
    -o-transform: scale(1.02);
    -ms-transform: scale(1.02);
  }
  100% {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@keyframes fadeIn {
  0% {
    opacity: 0;
    -webkit-opacity: 0;
    -moz-opacity: 0;
    filter: blur(12px);
    transform: scale(1.02);
    -webkit-transform: scale(1.02);
    -khtml-transform: scale(1.02);
    -moz-transform: scale(1.02);
    -o-transform: scale(1.02);
    -ms-transform: scale(1.02);
  }
  100% {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
.cover-wrapper .cover-body {
  z-index: 1;
  position: relative;
  width: 100%;
  height: 100%;
}
.cover-wrapper#full {
  height: calc(100vh + 100px);
  padding-bottom: 100px;
}
.cover-wrapper#half {
  max-height: 640px;
  min-height: 400px;
  height: calc(36vh - 64px + 200px);
}
.cover-wrapper #scroll-down {
  width: 100%;
  height: 64px;
  position: absolute;
  bottom: 100px;
  text-align: center;
  cursor: pointer;
}
.cover-wrapper #scroll-down .scroll-down-effects {
  color: #fff;
  font-size: 24px;
  line-height: 64px;
  position: absolute;
  width: 24px;
  left: calc(50% - 12px);
  text-shadow: 0 1px 2px rgba(0,0,0,0.1);
  animation: scroll-down-effect 1.5s infinite;
  -webkit-animation: scroll-down-effect 1.5s infinite;
  -khtml-animation: scroll-down-effect 1.5s infinite;
  -moz-animation: scroll-down-effect 1.5s infinite;
  -o-animation: scroll-down-effect 1.5s infinite;
  -ms-animation: scroll-down-effect 1.5s infinite;
}
@-moz-keyframes scroll-down-effect {
  0% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
  50% {
    top: -16px;
    opacity: 0.4;
    -webkit-opacity: 0.4;
    -moz-opacity: 0.4;
  }
  100% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@-webkit-keyframes scroll-down-effect {
  0% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
  50% {
    top: -16px;
    opacity: 0.4;
    -webkit-opacity: 0.4;
    -moz-opacity: 0.4;
  }
  100% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@-o-keyframes scroll-down-effect {
  0% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
  50% {
    top: -16px;
    opacity: 0.4;
    -webkit-opacity: 0.4;
    -moz-opacity: 0.4;
  }
  100% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@keyframes scroll-down-effect {
  0% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
  50% {
    top: -16px;
    opacity: 0.4;
    -webkit-opacity: 0.4;
    -moz-opacity: 0.4;
  }
  100% {
    top: 0;
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
.cover-wrapper .cover-body {
  margin-top: 64px;
  margin-bottom: 100px;
}
.cover-wrapper .cover-body,
.cover-wrapper .cover-body .top,
.cover-wrapper .cover-body .bottom {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  -webkit-box-direction: normal;
  -moz-box-direction: normal;
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
  -webkit-flex-direction: column;
  -ms-flex-direction: column;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  -webkit-justify-content: center;
  -khtml-justify-content: center;
  -moz-justify-content: center;
  -o-justify-content: center;
  -ms-justify-content: center;
  max-width: 100%;
}
.cover-wrapper .cover-body .bottom {
  margin-top: 32px;
}
.cover-wrapper .cover-body .title {
  font-family: "Varela Round", "PingFang SC", "Microsoft YaHei", Helvetica, Arial, Helvetica, monospace;
  font-size: 3.125rem;
  line-height: 1.2;
  text-shadow: 0 1px 2px rgba(0,0,0,0.1);
}
.cover-wrapper .cover-body .subtitle {
  font-size: 20px;
}
.cover-wrapper .cover-body .logo {
  max-height: 120px;
  max-width: calc(100% - 4 * 16px);
}
@media screen and (min-height: 1024px) {
  .cover-wrapper .cover-body .title {
    font-size: 3rem;
  }
  .cover-wrapper .cover-body .subtitle {
    font-size: 1.05rem;
  }
  .cover-wrapper .cover-body .logo {
    max-height: 150px;
  }
}
.cover-wrapper .cover-body .m_search {
  position: relative;
  max-width: calc(100% - 16px);
  width: 320px;
  vertical-align: middle;
}
.cover-wrapper .cover-body .m_search .form {
  position: relative;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  width: 100%;
}
.cover-wrapper .cover-body .m_search .icon,
.cover-wrapper .cover-body .m_search .input {
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
.cover-wrapper .cover-body .m_search .icon {
  position: absolute;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  line-height: 2.5rem;
  width: 32px;
  top: 0;
  left: 5px;
  color: rgba(68,68,68,0.75);
}
.cover-wrapper .cover-body .m_search .input {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  height: 2.5rem;
  width: 100%;
  box-shadow: none;
  -webkit-box-shadow: none;
  box-sizing: border-box;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  font-size: 0.875rem;
  -webkit-appearance: none;
  padding-left: 36px;
  border-radius: 1.4rem;
  -webkit-border-radius: 1.4rem;
  background: rgba(255,255,255,0.6);
  backdrop-filter: blur(10px);
  border: none;
  color: var(--color-text);
}
@media screen and (max-width: 500px) {
  .cover-wrapper .cover-body .m_search .input {
    padding-left: 36px;
  }
}
.cover-wrapper .cover-body .m_search .input:hover {
  background: rgba(255,255,255,0.8);
}
.cover-wrapper .cover-body .m_search .input:focus {
  background: #fff;
}
.cover-wrapper .list-h {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  -webkit-box-direction: normal;
  -moz-box-direction: normal;
  -webkit-box-orient: horizontal;
  -moz-box-orient: horizontal;
  -webkit-flex-direction: row;
  -ms-flex-direction: row;
  flex-direction: row;
  flex-wrap: wrap;
  -webkit-flex-wrap: wrap;
  -khtml-flex-wrap: wrap;
  -moz-flex-wrap: wrap;
  -o-flex-wrap: wrap;
  -ms-flex-wrap: wrap;
  align-items: stretch;
  border-radius: 4px;
  -webkit-border-radius: 4px;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
}
.cover-wrapper .list-h a {
  -webkit-box-flex: 1;
  -moz-box-flex: 1;
  -webkit-flex: 1 0;
  -ms-flex: 1 0;
  flex: 1 0;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  font-weight: 600;
}
.cover-wrapper .list-h a img {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  border-radius: 2px;
  -webkit-border-radius: 2px;
  margin: 4px;
  min-width: 40px;
  max-width: 44px;
}
@media screen and (max-width: 768px) {
  .cover-wrapper .list-h a img {
    min-width: 36px;
    max-width: 40px;
  }
}
@media screen and (max-width: 500px) {
  .cover-wrapper .list-h a img {
    margin: 2px 4px;
    min-width: 32px;
    max-width: 36px;
  }
}
@media screen and (max-width: 375px) {
  .cover-wrapper .list-h a img {
    min-width: 28px;
    max-width: 32px;
  }
}
.cover-wrapper {
  max-width: 100%;
}
.cover-wrapper.search .bottom .menu {
  margin-top: 16px;
}
.cover-wrapper.search .bottom .menu .list-h a {
  white-space: nowrap;
  -webkit-box-direction: normal;
  -moz-box-direction: normal;
  -webkit-box-orient: horizontal;
  -moz-box-orient: horizontal;
  -webkit-flex-direction: row;
  -ms-flex-direction: row;
  flex-direction: row;
  align-items: baseline;
  padding: 2px;
  margin: 4px;
  color: var(--color-site-inner);
  opacity: 0.75;
  -webkit-opacity: 0.75;
  -moz-opacity: 0.75;
  text-shadow: 0 1px 2px rgba(0,0,0,0.05);
  border-bottom: 2px solid transparent;
}
.cover-wrapper.search .bottom .menu .list-h a i {
  margin-right: 4px;
}
.cover-wrapper.search .bottom .menu .list-h a p {
  font-size: 0.9375rem;
}
.cover-wrapper.search .bottom .menu .list-h a:hover,
.cover-wrapper.search .bottom .menu .list-h a.active,
.cover-wrapper.search .bottom .menu .list-h a:active {
  opacity: 1;
  -webkit-opacity: 1;
  -moz-opacity: 1;
  border-bottom: 2px solid var(--color-site-inner);
}
.cover-wrapper.dock .menu,
.cover-wrapper.featured .menu,
.cover-wrapper.focus .menu {
  border-radius: 6px;
  -webkit-border-radius: 6px;
}
.cover-wrapper.dock .menu .list-h a,
.cover-wrapper.featured .menu .list-h a,
.cover-wrapper.focus .menu .list-h a {
  -webkit-box-direction: normal;
  -moz-box-direction: normal;
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
  -webkit-flex-direction: column;
  -ms-flex-direction: column;
  flex-direction: column;
  align-items: center;
  padding: 12px;
  line-height: 24px;
  border-radius: 4px;
  -webkit-border-radius: 4px;
  border-bottom: none;
  text-align: center;
  align-content: flex-end;
  color: rgba(68,68,68,0.7);
  font-size: 1.5rem;
}
@media screen and (max-width: 500px) {
  .cover-wrapper.dock .menu .list-h a,
  .cover-wrapper.featured .menu .list-h a,
  .cover-wrapper.focus .menu .list-h a {
    padding: 12px 8px;
  }
}
.cover-wrapper.dock .menu .list-h a i,
.cover-wrapper.featured .menu .list-h a i,
.cover-wrapper.focus .menu .list-h a i {
  margin: 8px;
}
.cover-wrapper.dock .menu .list-h a p,
.cover-wrapper.featured .menu .list-h a p,
.cover-wrapper.focus .menu .list-h a p {
  font-size: 0.875rem;
}
.cover-wrapper.dock .menu .list-h a.active,
.cover-wrapper.featured .menu .list-h a.active,
.cover-wrapper.focus .menu .list-h a.active {
  background: var(--color-card);
  backdrop-filter: none;
}
.cover-wrapper.dock .menu .list-h a.active i,
.cover-wrapper.featured .menu .list-h a.active i,
.cover-wrapper.focus .menu .list-h a.active i,
.cover-wrapper.dock .menu .list-h a.active i+p,
.cover-wrapper.featured .menu .list-h a.active i+p,
.cover-wrapper.focus .menu .list-h a.active i+p {
  color: #3dd9b6;
}
.cover-wrapper.dock .menu .list-h a.active img+p,
.cover-wrapper.featured .menu .list-h a.active img+p,
.cover-wrapper.focus .menu .list-h a.active img+p {
  color: var(--color-text);
}
.cover-wrapper.dock .menu .list-h a:hover,
.cover-wrapper.featured .menu .list-h a:hover,
.cover-wrapper.focus .menu .list-h a:hover {
  background: var(--color-card);
}
.cover-wrapper.dock .top {
  margin-bottom: 48px;
}
.cover-wrapper.dock .menu {
  background: rgba(255,255,255,0.5);
  position: absolute;
  bottom: 0;
  max-width: 100%;
}
.cover-wrapper.dock .menu .list-h {
  flex-wrap: nowrap;
  -webkit-flex-wrap: nowrap;
  -khtml-flex-wrap: nowrap;
  -moz-flex-wrap: nowrap;
  -o-flex-wrap: nowrap;
  -ms-flex-wrap: nowrap;
  margin: 4px;
}
.cover-wrapper.dock .menu .list-h a+a {
  margin-left: 4px;
}
@media screen and (max-width: 500px) {
  .cover-wrapper.dock .menu .list-h {
    overflow-x: scroll;
  }
  .cover-wrapper.dock .menu .list-h::-webkit-scrollbar {
    height: 0;
    width: 0;
  }
  .cover-wrapper.dock .menu .list-h::-webkit-scrollbar-track-piece {
    background: transparent;
  }
  .cover-wrapper.dock .menu .list-h::-webkit-scrollbar-thumb {
    background: #3dd9b6;
    cursor: pointer;
    border-radius: 0;
    -webkit-border-radius: 0;
  }
  .cover-wrapper.dock .menu .list-h::-webkit-scrollbar-thumb:hover {
    background: #ff5722;
  }
}
@supports (backdrop-filter: blur(20px)) {
  .cover-wrapper.dock .menu {
    background: rgba(255,255,255,0.5);
    backdrop-filter: saturate(200%) blur(20px);
  }
}
@font-face {
  font-family: 'UbuntuMono';
  src: url("https://unpkg.com/volantis-static@0.0.1654736714924/media/fonts/UbuntuMono/UbuntuMono-Regular.ttf");
  font-weight: 'normal';
  font-style: 'normal';
  font-display: swap;
}
@font-face {
  font-family: 'Varela Round';
  src: url("https://unpkg.com/volantis-static@0.0.1654736714924/media/fonts/VarelaRound/VarelaRound-Regular.ttf");
  font-weight: 'normal';
  font-style: 'normal';
  font-display: swap;
}
.l_header {
  position: fixed;
  z-index: 1000;
  top: 0;
  width: 100%;
  height: 64px;
  background: var(--color-card);
  box-shadow: 0 1px 2px 0px rgba(0,0,0,0.1);
  -webkit-box-shadow: 0 1px 2px 0px rgba(0,0,0,0.1);
}
.l_header.auto {
  transition: opacity 0.4s ease;
  -webkit-transition: opacity 0.4s ease;
  -khtml-transition: opacity 0.4s ease;
  -moz-transition: opacity 0.4s ease;
  -o-transition: opacity 0.4s ease;
  -ms-transition: opacity 0.4s ease;
  visibility: hidden;
}
.l_header.auto.show {
  opacity: 1 !important;
  -webkit-opacity: 1 !important;
  -moz-opacity: 1 !important;
  visibility: visible;
}
.l_header .container {
  margin-left: 16px;
  margin-right: 16px;
}
.l_header #wrapper {
  height: 100%;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
}
.l_header #wrapper .nav-main,
.l_header #wrapper .nav-sub {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  flex-wrap: nowrap;
  -webkit-flex-wrap: nowrap;
  -khtml-flex-wrap: nowrap;
  -moz-flex-wrap: nowrap;
  -o-flex-wrap: nowrap;
  -ms-flex-wrap: nowrap;
  justify-content: space-between;
  -webkit-justify-content: space-between;
  -khtml-justify-content: space-between;
  -moz-justify-content: space-between;
  -o-justify-content: space-between;
  -ms-justify-content: space-between;
  align-items: center;
}
.l_header #wrapper .nav-main {
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
.l_header #wrapper.sub .nav-main {
  transform: translateY(-64px);
  -webkit-transform: translateY(-64px);
  -khtml-transform: translateY(-64px);
  -moz-transform: translateY(-64px);
  -o-transform: translateY(-64px);
  -ms-transform: translateY(-64px);
}
.l_header #wrapper .nav-sub {
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
  opacity: 0;
  -webkit-opacity: 0;
  -moz-opacity: 0;
  height: 64px;
  width: calc(100% - 2 * 16px);
  position: absolute;
}
.l_header #wrapper .nav-sub ::-webkit-scrollbar {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
}
@media screen and (min-width: 2048px) {
  .l_header #wrapper .nav-sub {
    max-width: 55vw;
    margin: auto;
  }
}
.l_header #wrapper.sub .nav-sub {
  opacity: 1;
  -webkit-opacity: 1;
  -moz-opacity: 1;
}
.l_header #wrapper .title {
  position: relative;
  color: var(--color-text);
  padding-left: 24px;
  max-height: 64px;
}
.l_header #wrapper .nav-main .title {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  flex-shrink: 0;
  line-height: 64px;
  padding: 0 24px;
  font-size: 1.25rem;
  font-family: "Varela Round", "PingFang SC", "Microsoft YaHei", Helvetica, Arial, Helvetica, monospace;
}
.l_header #wrapper .nav-main .title img {
  height: 64px;
}
.l_header .nav-sub {
  max-width: 1080px;
  margin: auto;
}
.l_header .nav-sub .title {
  font-weight: bold;
  font-family: UbuntuMono, "Varela Round", "PingFang SC", "Microsoft YaHei", Helvetica, Arial, Menlo, Monaco, monospace, sans-serif;
  line-height: 1.2;
  max-height: 64px;
  white-space: normal;
  flex-shrink: 1;
}
.l_header .switcher {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
  line-height: 64px;
  align-items: center;
}
.l_header .switcher .s-toc {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
}
@media screen and (max-width: 768px) {
  .l_header .switcher .s-toc {
    display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
    display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
    display: -ms-flexbox /* TWEENER - IE 10 */;
    display: -webkit-flex /* NEW - Chrome */;
    display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
    display: flex;
  }
}
.l_header .switcher >li {
  height: 48px;
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
  margin: 2px;
}
@media screen and (max-width: 500px) {
  .l_header .switcher >li {
    margin: 0 1px;
    height: 48px;
  }
}
.l_header .switcher >li >a {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  justify-content: center;
  -webkit-justify-content: center;
  -khtml-justify-content: center;
  -moz-justify-content: center;
  -o-justify-content: center;
  -ms-justify-content: center;
  align-items: center;
  width: 48px;
  height: 48px;
  padding: 0.85em 1.1em;
  border-radius: 100px;
  -webkit-border-radius: 100px;
  border: none;
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
  color: #3dd9b6;
}
.l_header .switcher >li >a:hover {
  border: none;
}
.l_header .switcher >li >a.active,
.l_header .switcher >li >a:active {
  border: none;
  background: var(--color-site-bg);
}
@media screen and (max-width: 500px) {
  .l_header .switcher >li >a {
    width: 36px;
    height: 48px;
  }
}
.l_header .nav-sub .switcher {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
}
.l_header .m_search {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  height: 64px;
  width: 240px;
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
@media screen and (max-width: 1024px) {
  .l_header .m_search {
    width: 44px;
    min-width: 44px;
  }
  .l_header .m_search input::placeholder {
    opacity: 0;
    -webkit-opacity: 0;
    -moz-opacity: 0;
  }
  .l_header .m_search:hover {
    width: 240px;
  }
  .l_header .m_search:hover input::placeholder {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@media screen and (min-width: 500px) {
  .l_header .m_search:hover .input {
    width: 100%;
  }
  .l_header .m_search:hover .input::placeholder {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
@media screen and (max-width: 500px) {
  .l_header .m_search {
    min-width: 0;
  }
  .l_header .m_search input::placeholder {
    opacity: 1;
    -webkit-opacity: 1;
    -moz-opacity: 1;
  }
}
.l_header .m_search .form {
  position: relative;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  width: 100%;
  align-items: center;
}
.l_header .m_search .icon {
  position: absolute;
  width: 36px;
  left: 5px;
  color: var(--color-meta);
}
@media screen and (max-width: 500px) {
  .l_header .m_search .icon {
    display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
    display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
    display: none;
  }
}
.l_header .m_search .input {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  padding-top: 8px;
  padding-bottom: 8px;
  line-height: 1.3;
  width: 100%;
  color: var(--color-text);
  background: #fafafa;
  box-shadow: none;
  -webkit-box-shadow: none;
  box-sizing: border-box;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  padding-left: 40px;
  font-size: 0.875rem;
  border-radius: 8px;
  -webkit-border-radius: 8px;
  border: none;
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
@media screen and (min-width: 500px) {
  .l_header .m_search .input:focus {
    box-shadow: 0 4px 8px 0px rgba(0,0,0,0.1);
    -webkit-box-shadow: 0 4px 8px 0px rgba(0,0,0,0.1);
  }
}
@media screen and (max-width: 500px) {
  .l_header .m_search .input {
    background: var(--color-block);
    padding-left: 8px;
    border: none;
  }
  .l_header .m_search .input:hover,
  .l_header .m_search .input:focus {
    border: none;
  }
}
@media (max-width: 500px) {
  .l_header .m_search {
    left: 0;
    width: 0;
    overflow: hidden;
    position: absolute;
    background: #fff;
    transition: all 0.28s ease;
    -webkit-transition: all 0.28s ease;
    -khtml-transition: all 0.28s ease;
    -moz-transition: all 0.28s ease;
    -o-transition: all 0.28s ease;
    -ms-transition: all 0.28s ease;
  }
  .l_header .m_search .input {
    border-radius: 32px;
    -webkit-border-radius: 32px;
    margin-left: 16px;
    padding-left: 16px;
  }
  .l_header.z_search-open .m_search {
    width: 100%;
  }
  .l_header.z_search-open .m_search .input {
    width: calc(100% - 120px);
  }
}
ul.m-pc >li>a {
  color: inherit;
  border-bottom: 2px solid transparent;
}
ul.m-pc >li>a:active,
ul.m-pc >li>a.active {
  border-bottom: 2px solid #3dd9b6;
}
ul.m-pc li:hover >ul.list-v,
ul.list-v li:hover >ul.list-v {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
}
ul.nav-list-h {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: -ms-flexbox /* TWEENER - IE 10 */;
  display: -webkit-flex /* NEW - Chrome */;
  display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
  display: flex;
  align-items: stretch;
}
ul.nav-list-h>li {
  position: relative;
  justify-content: center;
  -webkit-justify-content: center;
  -khtml-justify-content: center;
  -moz-justify-content: center;
  -o-justify-content: center;
  -ms-justify-content: center;
  height: 100%;
  line-height: 2.4;
  border-radius: 4px;
  -webkit-border-radius: 4px;
}
ul.nav-list-h>li >a {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-weight: 600;
}
ul.list-v {
  z-index: 1;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
  position: absolute;
  background: var(--color-card);
  box-shadow: 0 2px 4px 0px rgba(0,0,0,0.08), 0 4px 8px 0px rgba(0,0,0,0.08), 0 8px 16px 0px rgba(0,0,0,0.08);
  -webkit-box-shadow: 0 2px 4px 0px rgba(0,0,0,0.08), 0 4px 8px 0px rgba(0,0,0,0.08), 0 8px 16px 0px rgba(0,0,0,0.08);
  margin-top: -6px;
  border-radius: 4px;
  -webkit-border-radius: 4px;
  padding: 8px 0;
}
ul.list-v.show {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
}
ul.list-v hr {
  margin-top: 8px;
  margin-bottom: 8px;
}
ul.list-v >li {
  white-space: nowrap;
  word-break: keep-all;
}
ul.list-v >li.header {
  font-size: 0.78125rem;
  font-weight: bold;
  line-height: 2em;
  color: var(--color-meta);
  margin: 8px 16px 4px;
}
ul.list-v >li.header i {
  margin-right: 8px;
}
ul.list-v >li ul {
  margin-left: 0;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
  margin-top: -40px;
}
ul.list-v .aplayer-container {
  min-height: 64px;
  padding: 6px 16px;
}
ul.list-v >li>a {
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  color: var(--color-list);
  font-size: 0.875rem;
  font-weight: bold;
  line-height: 36px;
  padding: 0 20px 0 16px;
  text-overflow: ellipsis;
  margin: 0 4px;
  border-radius: 4px;
  -webkit-border-radius: 4px;
}
@media screen and (max-width: 1024px) {
  ul.list-v >li>a {
    line-height: 40px;
  }
}
ul.list-v >li>a >i {
  margin-right: 8px;
}
ul.list-v >li>a:active,
ul.list-v >li>a.active {
  color: var(--color-list-hl);
}
ul.list-v >li>a:hover {
  color: var(--color-list-hl);
  background: var(--color-site-bg);
}
.l_header .menu >ul>li>a {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: block;
  padding: 0 8px;
}
.l_header .menu >ul>li>a >i {
  margin-right: 4px;
}
.l_header ul.nav-list-h>li {
  color: var(--color-list);
  line-height: 64px;
}
.l_header ul.nav-list-h>li >a {
  max-height: 64px;
  overflow: hidden;
  color: inherit;
}
.l_header ul.nav-list-h>li >a:active,
.l_header ul.nav-list-h>li >a.active {
  color: #3dd9b6;
}
.l_header ul.nav-list-h>li:hover>a {
  color: var(--color-list-hl);
}
.l_header ul.nav-list-h>li i.music {
  animation: rotate-effect 1.5s linear infinite;
  -webkit-animation: rotate-effect 1.5s linear infinite;
  -khtml-animation: rotate-effect 1.5s linear infinite;
  -moz-animation: rotate-effect 1.5s linear infinite;
  -o-animation: rotate-effect 1.5s linear infinite;
  -ms-animation: rotate-effect 1.5s linear infinite;
}
@-moz-keyframes rotate-effect {
  0% {
    transform: rotate(0);
    -webkit-transform: rotate(0);
    -khtml-transform: rotate(0);
    -moz-transform: rotate(0);
    -o-transform: rotate(0);
    -ms-transform: rotate(0);
  }
  25% {
    transform: rotate(90deg);
    -webkit-transform: rotate(90deg);
    -khtml-transform: rotate(90deg);
    -moz-transform: rotate(90deg);
    -o-transform: rotate(90deg);
    -ms-transform: rotate(90deg);
  }
  50% {
    transform: rotate(180deg);
    -webkit-transform: rotate(180deg);
    -khtml-transform: rotate(180deg);
    -moz-transform: rotate(180deg);
    -o-transform: rotate(180deg);
    -ms-transform: rotate(180deg);
  }
  75% {
    transform: rotate(270deg);
    -webkit-transform: rotate(270deg);
    -khtml-transform: rotate(270deg);
    -moz-transform: rotate(270deg);
    -o-transform: rotate(270deg);
    -ms-transform: rotate(270deg);
  }
  100% {
    transform: rotate(360deg);
    -webkit-transform: rotate(360deg);
    -khtml-transform: rotate(360deg);
    -moz-transform: rotate(360deg);
    -o-transform: rotate(360deg);
    -ms-transform: rotate(360deg);
  }
}
@-webkit-keyframes rotate-effect {
  0% {
    transform: rotate(0);
    -webkit-transform: rotate(0);
    -khtml-transform: rotate(0);
    -moz-transform: rotate(0);
    -o-transform: rotate(0);
    -ms-transform: rotate(0);
  }
  25% {
    transform: rotate(90deg);
    -webkit-transform: rotate(90deg);
    -khtml-transform: rotate(90deg);
    -moz-transform: rotate(90deg);
    -o-transform: rotate(90deg);
    -ms-transform: rotate(90deg);
  }
  50% {
    transform: rotate(180deg);
    -webkit-transform: rotate(180deg);
    -khtml-transform: rotate(180deg);
    -moz-transform: rotate(180deg);
    -o-transform: rotate(180deg);
    -ms-transform: rotate(180deg);
  }
  75% {
    transform: rotate(270deg);
    -webkit-transform: rotate(270deg);
    -khtml-transform: rotate(270deg);
    -moz-transform: rotate(270deg);
    -o-transform: rotate(270deg);
    -ms-transform: rotate(270deg);
  }
  100% {
    transform: rotate(360deg);
    -webkit-transform: rotate(360deg);
    -khtml-transform: rotate(360deg);
    -moz-transform: rotate(360deg);
    -o-transform: rotate(360deg);
    -ms-transform: rotate(360deg);
  }
}
@-o-keyframes rotate-effect {
  0% {
    transform: rotate(0);
    -webkit-transform: rotate(0);
    -khtml-transform: rotate(0);
    -moz-transform: rotate(0);
    -o-transform: rotate(0);
    -ms-transform: rotate(0);
  }
  25% {
    transform: rotate(90deg);
    -webkit-transform: rotate(90deg);
    -khtml-transform: rotate(90deg);
    -moz-transform: rotate(90deg);
    -o-transform: rotate(90deg);
    -ms-transform: rotate(90deg);
  }
  50% {
    transform: rotate(180deg);
    -webkit-transform: rotate(180deg);
    -khtml-transform: rotate(180deg);
    -moz-transform: rotate(180deg);
    -o-transform: rotate(180deg);
    -ms-transform: rotate(180deg);
  }
  75% {
    transform: rotate(270deg);
    -webkit-transform: rotate(270deg);
    -khtml-transform: rotate(270deg);
    -moz-transform: rotate(270deg);
    -o-transform: rotate(270deg);
    -ms-transform: rotate(270deg);
  }
  100% {
    transform: rotate(360deg);
    -webkit-transform: rotate(360deg);
    -khtml-transform: rotate(360deg);
    -moz-transform: rotate(360deg);
    -o-transform: rotate(360deg);
    -ms-transform: rotate(360deg);
  }
}
@keyframes rotate-effect {
  0% {
    transform: rotate(0);
    -webkit-transform: rotate(0);
    -khtml-transform: rotate(0);
    -moz-transform: rotate(0);
    -o-transform: rotate(0);
    -ms-transform: rotate(0);
  }
  25% {
    transform: rotate(90deg);
    -webkit-transform: rotate(90deg);
    -khtml-transform: rotate(90deg);
    -moz-transform: rotate(90deg);
    -o-transform: rotate(90deg);
    -ms-transform: rotate(90deg);
  }
  50% {
    transform: rotate(180deg);
    -webkit-transform: rotate(180deg);
    -khtml-transform: rotate(180deg);
    -moz-transform: rotate(180deg);
    -o-transform: rotate(180deg);
    -ms-transform: rotate(180deg);
  }
  75% {
    transform: rotate(270deg);
    -webkit-transform: rotate(270deg);
    -khtml-transform: rotate(270deg);
    -moz-transform: rotate(270deg);
    -o-transform: rotate(270deg);
    -ms-transform: rotate(270deg);
  }
  100% {
    transform: rotate(360deg);
    -webkit-transform: rotate(360deg);
    -khtml-transform: rotate(360deg);
    -moz-transform: rotate(360deg);
    -o-transform: rotate(360deg);
    -ms-transform: rotate(360deg);
  }
}
.menu-phone li ul.list-v {
  right: calc(100% - 0.5 * 16px);
}
.menu-phone li ul.list-v ul {
  right: calc(100% - 0.5 * 16px);
}
#wrapper {
  max-width: 1080px;
  margin: auto;
}
@media screen and (min-width: 2048px) {
  #wrapper {
    max-width: 55vw;
  }
}
#wrapper .menu {
  -webkit-box-flex: 1;
  -moz-box-flex: 1;
  -webkit-flex: 1 1;
  -ms-flex: 1 1;
  flex: 1 1;
  margin: 0 16px 0 0;
}
#wrapper .menu .list-v ul {
  left: calc(100% - 0.5 * 16px);
}
.menu-phone {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
  margin-top: 16px;
  right: 8px;
  transition: all 0.28s ease;
  -webkit-transition: all 0.28s ease;
  -khtml-transition: all 0.28s ease;
  -moz-transition: all 0.28s ease;
  -o-transition: all 0.28s ease;
  -ms-transition: all 0.28s ease;
}
.menu-phone ul {
  right: calc(100% - 0.5 * 16px);
}
@media screen and (max-width: 500px) {
  .menu-phone {
    display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
    display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
    display: block;
  }
}
.l_header {
  max-width: 65vw;
  left: calc((100% - 65vw) * 0.5);
  border-bottom-left-radius: 8px;
  border-bottom-right-radius: 8px;
}
@media screen and (max-width: 2048px) {
  .l_header {
    max-width: 1112px;
    left: calc((100% - 1112px) * 0.5);
  }
}
@media screen and (max-width: 1112px) {
  .l_header {
    left: 0;
    border-radius: 0;
    -webkit-border-radius: 0;
    max-width: 100%;
  }
}
@media screen and (max-width: 500px) {
  .l_header .container {
    margin-left: 0;
    margin-right: 0;
  }
  .l_header #wrapper .nav-main .title {
    padding-left: 16px;
    padding-right: 16px;
  }
  .l_header #wrapper .nav-sub {
    width: 100%;
  }
  .l_header #wrapper .nav-sub .title {
    overflow-y: scroll;
    margin-top: 2px;
    padding: 8px 16px;
  }
  .l_header #wrapper .switcher {
    display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
    display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
    display: -ms-flexbox /* TWEENER - IE 10 */;
    display: -webkit-flex /* NEW - Chrome */;
    display: flex /* NEW, Spec - Opera 12.1, Firefox 20+ */;
    display: flex;
    margin-right: 8px;
  }
  .l_header .menu {
    display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
    display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
    display: none;
  }
}
@media screen and (max-width: 500px) {
  .list-v li {
    max-width: 270px;
  }
}
#u-search {
  display: -webkit-box /* OLD - iOS 6-, Safari 3.1-6 */;
  display: -moz-box /* OLD - Firefox 19- (buggy but mostly works) */;
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  padding: 60px 20px;
  z-index: 1001;
}
@media screen and (max-width: 680px) {
  #u-search {
    padding: 0px;
  }
}

  </style>
  <link rel="stylesheet" href="/css/style.css" media="print" onload="this.media='all';this.onload=null">
  <noscript><link rel="stylesheet" href="/css/style.css"></noscript>
  
<script>
if (/*@cc_on!@*/false || (!!window.MSInputMethodContext && !!document.documentMode))
    document.write(
	'<style>'+
		'html{'+
			'overflow-x: hidden !important;'+
			'overflow-y: hidden !important;'+
		'}'+
		'.kill-ie{'+
			'text-align:center;'+
			'height: 100%;'+
			'margin-top: 15%;'+
			'margin-bottom: 5500%;'+
		'}'+
    '.kill-t{'+
      'font-size: 2rem;'+
    '}'+
    '.kill-c{'+
      'font-size: 1.2rem;'+
    '}'+
		'#l_header,#l_body{'+
			'display: none;'+
		'}'+
	'</style>'+
    '<div class="kill-ie">'+
        `<span class="kill-t"><b>Sorry, your browser cannot access this site</b></span><br/>`+
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    '</div>');
</script>


<noscript>
	<style>
		html{
			overflow-x: hidden !important;
			overflow-y: hidden !important;
		}
		.kill-noscript{
			text-align:center;
			height: 100%;
			margin-top: 15%;
			margin-bottom: 5500%;
		}
    .kill-t{
      font-size: 2rem;
    }
    .kill-c{
      font-size: 1.2rem;
    }
		#l_header,#l_body{
			display: none;
		}
	</style>
    <div class="kill-noscript">
        <span class="kill-t"><b>Sorry, your browser cannot access this site</b></span><br/>
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        <a target="_blank" rel="noopener" href="https://www.baidu.com/s?wd=启用JavaScript"><strong>Learn more ></strong></a>
    </div>
</noscript>


  <script>
  /************这个文件存放不需要重载的全局变量和全局函数*********/
  window.volantis = {}; // volantis 全局变量
  volantis.debug = "env"; // 调试模式
  volantis.dom = {}; // 页面Dom see: /source/js/app.js etc.

  volantis.GLOBAL_CONFIG ={
    debug: "env",
    cdn: {"js":{"app":"/js/app.js","parallax":"/js/plugins/parallax.js","rightMenu":"/js/plugins/rightMenu.js","rightMenus":"/js/plugins/rightMenus.js","sites":"/js/plugins/tags/sites.js","friends":"/js/plugins/tags/friends.js","contributors":"/js/plugins/tags/contributors.js","search":"/js/search/hexo.js"},"css":{"style":"/css/style.css"}},
    default: {"avatar":"https://unpkg.com/volantis-static@0.0.1654736714924/media/placeholder/avatar/round/3442075.svg","link":"https://unpkg.com/volantis-static@0.0.1654736714924/media/placeholder/link/8f277b4ee0ecd.svg","cover":"https://unpkg.com/volantis-static@0.0.1654736714924/media/placeholder/cover/76b86c0226ffd.svg","image":"https://unpkg.com/volantis-static@0.0.1654736714924/media/placeholder/image/2659360.svg"},
    lastupdate: new Date(1739433735785),
    sidebar: {
      for_page: ["blogger","category","tagcloud","donate"],
      for_post: ["toc"],
      webinfo: {
        lastupd: {
          enable: true,
          friendlyShow: true
        },
        runtime: {
          data: "2020/01/01",
          unit: "天"
        }
      }
    },
    plugins: {
      message: {"enable":true,"css":"https://unpkg.com/volantis-static@0.0.1654736714924/libs/izitoast/dist/css/iziToast.min.css","js":"https://unpkg.com/volantis-static@0.0.1654736714924/libs/izitoast/dist/js/iziToast.min.js","icon":{"default":"fa-solid fa-info-circle light-blue","quection":"fa-solid fa-question-circle light-blue"},"time":{"default":5000,"quection":20000},"position":"topRight","transitionIn":"bounceInLeft","transitionOut":"fadeOutRight","titleColor":"var(--color-text)","messageColor":"var(--color-text)","backgroundColor":"var(--color-card)","zindex":2147483647,"copyright":{"enable":true,"title":"知识共享许可协议","message":"请遵守 CC BY-NC-SA 4.0 协议。","icon":"far fa-copyright light-blue"},"aplayer":{"enable":true,"play":"fa-solid fa-play","pause":"fa-solid fa-pause"},"rightmenu":{"enable":true,"notice":true}},
      fancybox: {"css":"https://unpkg.com/volantis-static@0.0.1654736714924/libs/@fancyapps/ui/dist/fancybox.css","js":"https://unpkg.com/volantis-static@0.0.1654736714924/libs/@fancyapps/ui/dist/fancybox.umd.js"},
      
      
      
    }
  }

  /******************** volantis.EventListener ********************************/
  // 事件监听器 see: /source/js/app.js
  volantis.EventListener = {}
  // 这里存放pjax切换页面时将被移除的事件监听器
  volantis.EventListener.list = []
  //构造方法
  function volantisEventListener(type, f, ele) {
    this.type = type
    this.f = f
    this.ele = ele
  }
  // 移除事件监听器
  volantis.EventListener.remove = () => {
    volantis.EventListener.list.forEach(function (i) {
      i.ele.removeEventListener(i.type, i.f, false)
    })
    volantis.EventListener.list = []
  }
  /******************** volantis.dom.$ ********************************/
  // 注：这里没有选择器，也没有forEach一次只处理一个dom，这里重新封装主题常用的dom方法，返回的是dom对象，对象包含了以下方法，同时保留dom的原生API
  function volantisDom(ele) {
    if (!ele) ele = document.createElement("div")
    this.ele = ele;
    // ==============================================================
    this.ele.find = (c) => {
      let q = this.ele.querySelector(c)
      if (q)
        return new volantisDom(q)
    }
    // ==============================================================
    this.ele.hasClass = (c) => {
      return this.ele.className.match(new RegExp('(\\s|^)' + c + '(\\s|$)'));
    }
    this.ele.addClass = (c) => {
      this.ele.classList.add(c);
      return this.ele
    }
    this.ele.removeClass = (c) => {
      this.ele.classList.remove(c);
      return this.ele
    }
    this.ele.toggleClass = (c) => {
      if (this.ele.hasClass(c)) {
        this.ele.removeClass(c)
      } else {
        this.ele.addClass(c)
      }
      return this.ele
    }
    // ==============================================================
    // 参数 r 为 true 表示pjax切换页面时事件监听器将被移除，false不移除
    this.ele.on = (c, f, r = 1) => {
      this.ele.addEventListener(c, f, false)
      if (r) {
        volantis.EventListener.list.push(new volantisEventListener(c, f, this.ele))
      }
      return this.ele
    }
    this.ele.click = (f, r) => {
      this.ele.on("click", f, r)
      return this.ele
    }
    this.ele.scroll = (f, r) => {
      this.ele.on("scroll", f, r)
      return this.ele
    }
    // ==============================================================
    this.ele.html = (c) => {
      // if(c=== undefined){
      //   return this.ele.innerHTML
      // }else{
      this.ele.innerHTML = c
      return this.ele
      // }
    }
    // ==============================================================
    this.ele.hide = (c) => {
      this.ele.style.display = "none"
      return this.ele
    }
    this.ele.show = (c) => {
      this.ele.style.display = "block"
      return this.ele
    }
    // ==============================================================
    return this.ele
  }
  volantis.dom.$ = (ele) => {
    return !!ele ? new volantisDom(ele) : null;
  }
  /******************** RunItem ********************************/
  function RunItem() {
    this.list = []; // 存放回调函数
    this.start = () => {
      for (var i = 0; i < this.list.length; i++) {
        this.list[i].run();
      }
    };
    this.push = (fn, name, setRequestAnimationFrame = true) => {
      let myfn = fn
      if (setRequestAnimationFrame) {
        myfn = ()=>{
          volantis.requestAnimationFrame(fn)
        }
      }
      var f = new Item(myfn, name);
      this.list.push(f);
    };
    this.remove = (name) =>{
      for (let index = 0; index < this.list.length; index++) {
        const e = this.list[index];
        if (e.name == name) {
          this.list.splice(index,1);
        }
      }
    }
    // 构造一个可以run的对象
    function Item(fn, name) {
      // 函数名称
      this.name = name || fn.name;
      // run方法
      this.run = () => {
        try {
          fn()
        } catch (error) {
          console.log(error);
        }
      };
    }
  }
  /******************** Pjax ********************************/
  // /layout/_plugins/pjax/index.ejs
  // volantis.pjax.send(callBack[,"callBackName"]) 传入pjax:send回调函数
  // volantis.pjax.push(callBack[,"callBackName"]) 传入pjax:complete回调函数
  // volantis.pjax.error(callBack[,"callBackName"]) 传入pjax:error回调函数
  volantis.pjax = {};
  volantis.pjax.method = {
    complete: new RunItem(),
    error: new RunItem(),
    send: new RunItem(),
  };
  volantis.pjax = Object.assign(volantis.pjax, {
    push: volantis.pjax.method.complete.push,
    error: volantis.pjax.method.error.push,
    send: volantis.pjax.method.send.push,
  });
  /******************** RightMenu ********************************/
  // volantis.rightmenu.handle(callBack[,"callBackName"]) 外部菜单项控制
  // 可在 volantis.mouseEvent 处获取右键事件
  volantis.rightmenu = {};
  volantis.rightmenu.method = {
    handle: new RunItem(),
  }
  volantis.rightmenu = Object.assign(volantis.rightmenu, {
    handle: volantis.rightmenu.method.handle.push,
  });
  /********************  Dark Mode  ********************************/
  // /layout/_partial/scripts/darkmode.ejs
  // volantis.dark.mode 当前模式 dark or light
  // volantis.dark.toggle() 暗黑模式触发器
  // volantis.dark.push(callBack[,"callBackName"]) 传入触发器回调函数
  volantis.dark = {};
  volantis.dark.method = {
    toggle: new RunItem(),
  };
  volantis.dark = Object.assign(volantis.dark, {
    push: volantis.dark.method.toggle.push,
  });
  /********************  Message  ********************************/
  // VolantisApp.message
  /********************  isMobile  ********************************/
  // /source/js/app.js
  // volantis.isMobile
  // volantis.isMobileOld
  /********************脚本动态加载函数********************************/
  // volantis.js(src, cb)  cb 可以传入onload回调函数 或者 JSON对象 例如: volantis.js("src", ()=>{}) 或 volantis.js("src", {defer:true,onload:()=>{}})
  // volantis.css(src)

  // 返回Promise对象，如下方法同步加载资源，这利于处理文件资源之间的依赖关系，例如：APlayer 需要在 MetingJS 之前加载
  // (async () => {
  //     await volantis.js("...theme.plugins.aplayer.js.aplayer...")
  //     await volantis.js("...theme.plugins.aplayer.js.meting...")
  // })();

  // 已经加入了setTimeout
  volantis.js = (src, cb) => {
    return new Promise(resolve => {
      setTimeout(function () {
        var HEAD = document.getElementsByTagName("head")[0] || document.documentElement;
        var script = document.createElement("script");
        script.setAttribute("type", "text/javascript");
        if (cb) {
          if (JSON.stringify(cb)) {
            for (let p in cb) {
              if (p == "onload") {
                script[p] = () => {
                  cb[p]()
                  resolve()
                }
              } else {
                script[p] = cb[p]
                script.onload = resolve
              }
            }
          } else {
            script.onload = () => {
              cb()
              resolve()
            };
          }
        } else {
          script.onload = resolve
        }
        script.setAttribute("src", src);
        HEAD.appendChild(script);
      });
    });
  }
  volantis.css = (src) => {
    return new Promise(resolve => {
      setTimeout(function () {
        var link = document.createElement('link');
        link.rel = "stylesheet";
        link.href = src;
        link.onload = resolve;
        document.getElementsByTagName("head")[0].appendChild(link);
      });
    });
  }
  /********************按需加载的插件********************************/
  // volantis.import.jQuery().then(()=>{})
  volantis.import = {
    jQuery: () => {
      if (typeof jQuery == "undefined") {
        return volantis.js("https://unpkg.com/volantis-static@0.0.1654736714924/libs/jquery/dist/jquery.min.js")
      } else {
        return new Promise(resolve => {
          resolve()
        });
      }
    }
  }
  /********************** requestAnimationFrame ********************************/
  // 1、requestAnimationFrame 会把每一帧中的所有 DOM 操作集中起来，在一次重绘或回流中就完成，并且重绘或回流的时间间隔紧紧跟随浏览器的刷新频率，一般来说，这个频率为每秒60帧。
  // 2、在隐藏或不可见的元素中，requestAnimationFrame 将不会进行重绘或回流，这当然就意味着更少的的 cpu，gpu 和内存使用量。
  volantis.requestAnimationFrame = (fn)=>{
    if (!window.requestAnimationFrame) {
      window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame;
    }
    window.requestAnimationFrame(fn)
  }
  /************************ layoutHelper *****************************************/
  volantis.layoutHelper = (helper, html, opt)=>{
    opt = Object.assign({clean:false, pjax:true}, opt)
    function myhelper(helper, html, clean) {
      volantis.tempDiv = document.createElement("div");
      volantis.tempDiv.innerHTML = html;
      let layoutHelper = document.querySelector("#layoutHelper-"+helper)
      if (layoutHelper) {
        if (clean) {
          layoutHelper.innerHTML = ""
        }
        layoutHelper.append(volantis.tempDiv);
      }
    }
    myhelper(helper, html, opt.clean)
    if (opt.pjax) {
      volantis.pjax.push(()=>{
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        Object
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    <h2 id="Object-is"><a href="#Object-is" class="headerlink" title="Object.is()"></a>Object.is()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// ES5判断两个值是否相等，有两种方法：相等运算符（==）和严格相等运算符（===）。</span></span><br><span class="line"><span class="comment">// 这两种方法都有缺点，前者会自动转换数据类型，后者判断NaN不等于自身，+0 等于 -0</span></span><br><span class="line"><span class="comment">// ES6新出了Object.is方法解决这个问题。</span></span><br><span class="line"><span class="comment">// 它与与严格相等运算符（===）基本一致，不会进行强制类型转换，不同之处只有两个：一是+0不等于-0，二是NaN等于自身。</span></span><br><span class="line"><span class="comment">// Object.is(obj1, obj2)方法用来判断两个值是否严格相等。它与严格比较运算符（===）的行为基本一致。</span></span><br><span class="line"><span class="comment">// 参数: obj1：需要比较的第一个值, obj2：需要比较的第二个值。</span></span><br><span class="line"><span class="comment">// 返回值: 返回两个参数是否相同的布尔值。</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Object.is()方法在处理NaN和+0、-0上和严格相等运算符不同。</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(+<span class="number">0</span> === -<span class="number">0</span>, <span class="title class_">Object</span>.<span class="title function_">is</span>(+<span class="number">0</span>, -<span class="number">0</span>)); <span class="comment">// true false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">NaN</span> === <span class="title class_">NaN</span>, <span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="title class_">NaN</span>, <span class="title class_">NaN</span>)); <span class="comment">// false true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Object.is()方法在以下情况会返回true。</span></span><br><span class="line"><span class="comment">// 两个值都是undefined, null, NaN, true, false。</span></span><br><span class="line"><span class="comment">// 两个值都是相同个数的字符并且按照相同顺序组成的字符串。</span></span><br><span class="line"><span class="comment">// 两个值都指向同一个对象。</span></span><br><span class="line"><span class="comment">// 两个值都是正零（+0）、都是负零（-0）和都是除零和NaN外的其他同一个数字。</span></span><br><span class="line"></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="literal">undefined</span>, <span class="literal">undefined</span>), <span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="literal">null</span>, <span class="literal">null</span>)); <span class="comment">// true true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="literal">true</span>, <span class="literal">true</span>), <span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="literal">false</span>, <span class="literal">false</span>)); <span class="comment">// true true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="variable language_">window</span>, <span class="variable language_">window</span>), <span class="title class_">Object</span>.<span class="title function_">is</span>([], [])); <span class="comment">// true false</span></span><br><span class="line"><span class="keyword">var</span> foo = &#123; <span class="attr">a</span>: <span class="number">1</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> bar = &#123; <span class="attr">a</span>: <span class="number">1</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(foo, foo), <span class="title class_">Object</span>.<span class="title function_">is</span>(foo, bar)); <span class="comment">// true false</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Case 2: Signed zero</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="number">0</span>, -<span class="number">0</span>), <span class="title class_">Object</span>.<span class="title function_">is</span>(+<span class="number">0</span>, -<span class="number">0</span>)); <span class="comment">// false false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(-<span class="number">0</span>, -<span class="number">0</span>), <span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="number">0n</span>, -<span class="number">0n</span>)); <span class="comment">// true true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Case 3: NaN</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="title class_">NaN</span>, <span class="number">0</span> / <span class="number">0</span>), <span class="title class_">Object</span>.<span class="title function_">is</span>(<span class="title class_">NaN</span>, <span class="title class_">Number</span>.<span class="property">NaN</span>)); <span class="comment">// true true</span></span><br><span class="line"><span class="keyword">if</span> (!<span class="title class_">Object</span>.<span class="property">is</span>) &#123;</span><br><span class="line">  <span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(<span class="title class_">Object</span>, <span class="string">&#x27;is&#x27;</span>, &#123;</span><br><span class="line">    <span class="title function_">value</span>(<span class="params">x, y</span>) &#123;</span><br><span class="line">      <span class="comment">// SameValue algorithm</span></span><br><span class="line">      <span class="keyword">if</span> (x === y) &#123;</span><br><span class="line">        <span class="comment">// 针对+0 不等于 -0的情况</span></span><br><span class="line">        <span class="keyword">return</span> x !== <span class="number">0</span> || <span class="number">1</span> / x === <span class="number">1</span> / y;</span><br><span class="line">      &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 针对NaN的情况</span></span><br><span class="line">        <span class="keyword">return</span> x !== x &amp;&amp; y !== y;</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="built_in">isNaN</span>(<span class="title class_">NaN</span>)); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="built_in">isNaN</span>(<span class="number">123</span>)); <span class="comment">// false</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// isNaN判断是NaN的时候会返回true，不是NaN的时候会返回false；</span></span><br><span class="line"><span class="comment">// 并且每次判断它会先将值转换成数值，然后进行判断，如果值是字符串的话就返回false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="built_in">isNaN</span>(<span class="string">&#x27;123abc&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="built_in">isNaN</span>(<span class="string">&#x27;123&#x27;</span>)); <span class="comment">// false</span></span><br></pre></td></tr></table></figure>

<h2 id="Object-defineProperties"><a href="#Object-defineProperties" class="headerlink" title="Object.defineProperties()"></a>Object.defineProperties()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.defineProperties</span></span><br><span class="line"><span class="comment">// 在一个对象上定义一个(多个)新的属性或修改原有属性，修改后的目标对象obj。</span></span><br><span class="line"><span class="comment">// 语法： Object.defineProperties (obj, props)</span></span><br><span class="line"><span class="comment">// obj: 将要被添加属性或修改属性的对象</span></span><br><span class="line"><span class="comment">// props: 该对象的一个(多个)键值对 定义了将要为对象添加或修改的属性的具体配置</span></span><br><span class="line"><span class="keyword">var</span> obj = &#123; <span class="attr">firstName</span>: <span class="string">&#x27;zhang&#x27;</span>, <span class="attr">lastName</span>: <span class="string">&#x27;san&#x27;</span> &#125;;</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> obj1 = <span class="title class_">Object</span>.<span class="title function_">defineProperties</span>(obj, &#123;</span><br><span class="line">  <span class="attr">fullName</span>: &#123;</span><br><span class="line">    <span class="comment">//设置内部属性相关特性</span></span><br><span class="line">    <span class="comment">//configurable:true,</span></span><br><span class="line">    <span class="title function_">get</span>(<span class="params"></span>) &#123;</span><br><span class="line">      <span class="keyword">return</span> <span class="variable language_">this</span>.<span class="property">firstName</span> + <span class="variable language_">this</span>.<span class="property">lastName</span>;</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="title function_">set</span>(<span class="params">data</span>) &#123;</span><br><span class="line">      str = data.<span class="title function_">split</span>(<span class="string">&#x27; &#x27;</span>);</span><br><span class="line">      <span class="variable language_">this</span>.<span class="property">firstName</span> = str[<span class="number">0</span>];</span><br><span class="line">      <span class="variable language_">this</span>.<span class="property">lastName</span> = str[<span class="number">1</span>];</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;);</span><br><span class="line">obj.<span class="property">fullName</span> = <span class="string">&#x27;li si&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;obj.fullName = &#x27;</span>, obj.<span class="property">fullName</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;obj = &#x27;</span>, obj);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;obj===obj1 为 &#x27;</span>, obj === obj1);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 在举例中 fullname 属于惰性求值。惰性求值 ： 表达式不在它被绑定到变量之后就立即求值，而是在该值被取用的时候求值。</span></span><br><span class="line"><span class="comment">// obj === obj1为true，表示 Object.defineProperties()返回的不是一个新的对象，而是修改后的目标对象</span></span><br><span class="line"><span class="comment">// 介绍 Object.defineProperties中的第二个可选参数 props 的属性描述符以及相应的属性名称</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//延续上个代码段</span></span><br><span class="line"><span class="keyword">var</span> d = <span class="title class_">Object</span>.<span class="title function_">getOwnPropertyDescriptor</span>(obj, <span class="string">&#x27;fullName&#x27;</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(d);</span><br><span class="line"><span class="comment">// [[Configurable]]</span></span><br><span class="line"><span class="comment">// 表示能否通过delete删除此属性，初始值为false，如果直接使用字面量定义对象，默认为true</span></span><br><span class="line"><span class="comment">// [[Enumerable]]</span></span><br><span class="line"><span class="comment">// 表示该属性是否可枚举，即是否通过for - in循环或Object.keys()返回属性, 初始值为false，</span></span><br><span class="line"><span class="comment">// 如果直接使用字面量定义对象，默认为true</span></span><br><span class="line"><span class="comment">// [[Get]]</span></span><br><span class="line"><span class="comment">// 一个给属性提供 getter 的方法(访问对象属性时调用的函数, 返回值就是当前属性的值)，</span></span><br><span class="line"><span class="comment">// 如果没有 getter 则为 undefined。该方法返回值被用作属性值。默认为 undefined</span></span><br><span class="line"><span class="comment">// [[Set]]</span></span><br><span class="line"><span class="comment">// 一个给属性提供 setter 的方法(给对象属性设置值时调用的函数)，如果没有 setter 则为 undefined。</span></span><br><span class="line"><span class="comment">// 该方法将接受唯一参数，并将该参数的新值分配给该属性。默认为 undefined</span></span><br></pre></td></tr></table></figure>


<h2 id="Object-getPrototypeOf"><a href="#Object-getPrototypeOf" class="headerlink" title="Object.getPrototypeOf()"></a>Object.getPrototypeOf()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.getPrototypeOf(obj)</span></span><br><span class="line"><span class="comment">// 返回指定对象的原型（内部[[Prototype]]属性的值）</span></span><br><span class="line"><span class="comment">// obj：要返回其原型的对象</span></span><br><span class="line"><span class="comment">// 返回值：给定对象的原型。如果没有继承属性，则返回 null</span></span><br><span class="line"><span class="keyword">var</span> proto = &#123;&#125;;</span><br><span class="line"><span class="keyword">var</span> obj = <span class="title class_">Object</span>.<span class="title function_">create</span>(proto);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(obj), <span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(obj) === proto); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> reg = <span class="regexp">/a/</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(reg),</span><br><span class="line">  <span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(reg) === <span class="title class_">RegExp</span>.<span class="property"><span class="keyword">prototype</span></span></span><br><span class="line">); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="keyword">new</span> <span class="title class_">Date</span>()),</span><br><span class="line">  <span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="keyword">new</span> <span class="title class_">Date</span>()) === <span class="title class_">Date</span>.<span class="property"><span class="keyword">prototype</span></span></span><br><span class="line">); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="title class_">Object</span>) === <span class="title class_">Function</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="title class_">Function</span>) === <span class="title class_">Function</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="title class_">Date</span>) === <span class="title class_">Function</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="title class_">Object</span>()) === <span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="title class_">Function</span>()) === <span class="title class_">Function</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="title class_">Date</span>()) === <span class="title class_">String</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="keyword">new</span> <span class="title class_">Object</span>()) === <span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(&#123;&#125;) === <span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="keyword">new</span> <span class="title class_">Function</span>()) === <span class="title class_">Function</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getPrototypeOf</span>(<span class="keyword">new</span> <span class="title class_">Date</span>()) === <span class="title class_">Date</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(&#123;&#125; == <span class="keyword">new</span> <span class="title class_">Object</span>()); <span class="comment">// false</span></span><br><span class="line"></span><br></pre></td></tr></table></figure>

<h2 id="Object-create"><a href="#Object-create" class="headerlink" title="Object.create()"></a>Object.create()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.create()方法接受两个参数:Object.create(obj,propertiesObject) ;</span></span><br><span class="line"><span class="comment">// obj:一个对象，应该是新创建的对象的原型。</span></span><br><span class="line"><span class="comment">// propertiesObject：可选。该参数对象是一组属性与值，该对象的属性名称将是新创建的对象的属性名称，</span></span><br><span class="line"><span class="comment">// 值是属性描述符（这些属性描述符的结构与Object.defineProperties()的第二个参数一样）。</span></span><br><span class="line"><span class="comment">// 注意：该参数对象不能是 undefined，</span></span><br><span class="line"><span class="comment">// 另外只有该对象中自身拥有的可枚举的属性才有效，也就是说该对象的原型链上属性是无效的。</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Object.create(obj1)就是将obj2创建为一个空对象并将他的隐式原型对象指向obj1</span></span><br><span class="line"><span class="keyword">let</span> obj1 = &#123; <span class="attr">a</span>: <span class="number">10</span>, <span class="attr">b</span>: <span class="number">20</span> &#125;;</span><br><span class="line"><span class="keyword">let</span> obj2 = <span class="title class_">Object</span>.<span class="title function_">create</span>(obj1);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj2, obj2.<span class="property">__proto__</span>, obj2.<span class="property">__proto__</span> === obj1);</span><br><span class="line"></span><br><span class="line"><span class="keyword">let</span> object1 = &#123; <span class="attr">A</span>: <span class="number">10</span>, <span class="attr">B</span>: <span class="number">20</span> &#125;;</span><br><span class="line"><span class="keyword">let</span> object2 = object1;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(object2, object2.<span class="property">__proto__</span>, object2.<span class="property">__proto__</span> === object1);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 特例 这时obj2没有原型对象</span></span><br><span class="line"><span class="comment">// Object.create(null) 创建的对象是一个空对象，</span></span><br><span class="line"><span class="comment">// 在该对象上没有继承 Object.prototype 原型链上的属性或者方法,</span></span><br><span class="line"><span class="comment">// 例如：toString(), hasOwnProperty()等方法</span></span><br><span class="line"><span class="keyword">let</span> obj3 = <span class="title class_">Object</span>.<span class="title function_">create</span>(<span class="literal">null</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj3, obj3.<span class="property">__proto__</span>); <span class="comment">// undefined</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> o = <span class="title class_">Object</span>.<span class="title function_">create</span>(<span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>, &#123;</span><br><span class="line">  <span class="comment">// foo会成为所创建对象的数据属性</span></span><br><span class="line">  <span class="attr">foo</span>: &#123;</span><br><span class="line">    <span class="attr">writable</span>: <span class="literal">true</span>,</span><br><span class="line">    <span class="attr">configurable</span>: <span class="literal">true</span>,</span><br><span class="line">    <span class="attr">value</span>: <span class="string">&#x27;hello&#x27;</span></span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="comment">// bar会成为所创建对象的访问器属性</span></span><br><span class="line">  <span class="attr">bar</span>: &#123;</span><br><span class="line">    <span class="attr">configurable</span>: <span class="literal">false</span>,</span><br><span class="line">    <span class="attr">get</span>: <span class="keyword">function</span> (<span class="params"></span>) &#123;</span><br><span class="line">      <span class="keyword">return</span> <span class="number">10</span>;</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="attr">set</span>: <span class="keyword">function</span> (<span class="params">value</span>) &#123;</span><br><span class="line">      <span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;Setting `o.bar` to&#x27;</span>, value);</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(o);</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> test1 = <span class="title class_">Object</span>.<span class="title function_">create</span>(<span class="literal">null</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1); <span class="comment">// &#123;&#125; No Properties</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 因为在bar中设置了configurable 使用set,get方法默认都是不起作用，所以bar值无法赋值或者获取</span></span><br><span class="line"><span class="comment">// 这里的o对象继承了 Object.prototype Object上的原型方法</span></span><br><span class="line"><span class="comment">// 我们可以 对象的 __proto__属性，来获取对象原型链上的方法 如：</span></span><br><span class="line"></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(o.<span class="property">__proto__</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span>); <span class="comment">// undefined</span></span><br><span class="line"><span class="comment">// 通过打印发现， 将&#123;&#125;点开，显示的是 No Properties ，也就是在对象本身不存在属性跟方法，原型链上也不存在属性和方法</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// new object()</span></span><br><span class="line"><span class="keyword">var</span> test1 = &#123; <span class="attr">x</span>: <span class="number">1</span> &#125;;</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> test2 = <span class="keyword">new</span> <span class="title class_">Object</span>(test1);</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> test3 = <span class="title class_">Object</span>.<span class="title function_">create</span>(test1);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test3); <span class="comment">// &#123;&#125;</span></span><br><span class="line"><span class="comment">// test3等价于test5</span></span><br><span class="line"><span class="keyword">var</span> test4 = <span class="keyword">function</span> (<span class="params"></span>) &#123;&#125;;</span><br><span class="line">test4.<span class="property"><span class="keyword">prototype</span></span> = test1;</span><br><span class="line"><span class="keyword">var</span> test5 = <span class="keyword">new</span> <span class="title function_">test4</span>();</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test5);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test5.<span class="property">__proto__</span> === test3.<span class="property">__proto__</span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2); <span class="comment">//&#123;x:1&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// &#123;&#125;是javascript对象字面量创建的形式，其本质和new Object()并无区别，默认都是继承了Object对象上的prototype</span></span><br><span class="line"><span class="keyword">var</span> test1 = &#123;&#125;;</span><br><span class="line"><span class="keyword">var</span> test2 = <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"><span class="keyword">var</span> test3 = <span class="title class_">Object</span>.<span class="title function_">create</span>(<span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>);</span><br><span class="line"><span class="keyword">var</span> test4 = <span class="title class_">Object</span>.<span class="title function_">create</span>(<span class="literal">null</span>); <span class="comment">// console.log(test4.__proto__)=&gt;undefined 没有继承原型属性和方法</span></span><br><span class="line"></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span> === <span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2.<span class="property">__proto__</span> === <span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span> === test2.<span class="property">__proto__</span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span> === test3.<span class="property">__proto__</span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2.<span class="property">__proto__</span> === test3.<span class="property">__proto__</span>); <span class="comment">// true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span> === test4.<span class="property">__proto__</span>); <span class="comment">// false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2.<span class="property">__proto__</span> === test4.<span class="property">__proto__</span>); <span class="comment">// false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test3.<span class="property">__proto__</span> === test4.<span class="property">__proto__</span>); <span class="comment">// false</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 总结：使用Object.create()是将对象继承到原型链上，然后可以通过对象实例的__proto__属性进行访问原型链上的属性</span></span><br><span class="line"><span class="keyword">var</span> test = <span class="title class_">Object</span>.<span class="title function_">create</span>(&#123; <span class="attr">x</span>: <span class="number">123</span>, <span class="attr">y</span>: <span class="number">345</span> &#125;);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test); <span class="comment">// &#123;&#125;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test.<span class="property">x</span>); <span class="comment">// 123</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test.<span class="property">__proto__</span>.<span class="property">x</span>); <span class="comment">// 123</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test.<span class="property">__proto__</span>.<span class="property">x</span> === test.<span class="property">x</span>); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> test1 = <span class="keyword">new</span> <span class="title class_">Object</span>(&#123; <span class="attr">x</span>: <span class="number">123</span>, <span class="attr">y</span>: <span class="number">345</span> &#125;);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1); <span class="comment">// &#123;x:123,y:345&#125;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">x</span>); <span class="comment">// 123</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span>.<span class="property">x</span>); <span class="comment">// undefined</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test1.<span class="property">__proto__</span>.<span class="property">x</span> === test1.<span class="property">x</span>); <span class="comment">// false</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> test2 = &#123; <span class="attr">x</span>: <span class="number">123</span>, <span class="attr">y</span>: <span class="number">345</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2); <span class="comment">// &#123;x:123,y:345&#125;;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2.<span class="property">x</span>); <span class="comment">// 123</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2.<span class="property">__proto__</span>.<span class="property">x</span>); <span class="comment">// undefined</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(test2.<span class="property">__proto__</span>.<span class="property">x</span> === test2.<span class="property">x</span>); <span class="comment">// false</span></span><br></pre></td></tr></table></figure>

<h2 id="Object-entries"><a href="#Object-entries" class="headerlink" title="Object.entries()"></a>Object.entries()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.entries() 方法返回一个给定对象自身可枚举属性的键值对数组。</span></span><br><span class="line"><span class="comment">// 其排列与使用 for...in 循环遍历该对象时返回的顺序一致（区别在于 for-in 循环还会枚举原型链中的属性）。</span></span><br><span class="line"><span class="comment">// 语法</span></span><br><span class="line"><span class="comment">// Object.entries(obj)</span></span><br><span class="line"><span class="comment">// 参数</span></span><br><span class="line"><span class="comment">// obj：可以返回其可枚举属性的键值对的对象。</span></span><br><span class="line"><span class="comment">// 返回值</span></span><br><span class="line"><span class="comment">// 给定对象自身可枚举属性的键值对数组。</span></span><br><span class="line"><span class="comment">// 描述</span></span><br><span class="line"><span class="comment">// Object.entries()返回一个数组，其元素是与直接在object上找到的可枚举属性键值对相对应的数组。</span></span><br><span class="line"><span class="comment">// 属性的顺序与通过手动循环对象的属性值所给出的顺序相同。</span></span><br><span class="line"><span class="comment">// 该方法返回对象 obj 自身的可枚举属性的键值对数组。结果是一个二维数组，</span></span><br><span class="line"><span class="comment">// 数组中的元素是一个由两个元素 key ，value 组成的数组。</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 参数为对象</span></span><br><span class="line"><span class="keyword">const</span> obj = &#123; <span class="attr">name</span>: <span class="string">&#x27;xiaoming&#x27;</span>, <span class="attr">age</span>: <span class="string">&#x27;seven&#x27;</span>, <span class="attr">sex</span>: <span class="string">&#x27;man&#x27;</span>, <span class="attr">grade</span>: <span class="string">&#x27;four&#x27;</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">entries</span>(obj));</span><br><span class="line"></span><br><span class="line"><span class="comment">// 参数为数组</span></span><br><span class="line"><span class="keyword">const</span> obj1 = [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>];</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">entries</span>(obj1));</span><br><span class="line"></span><br><span class="line"><span class="comment">// 参数为数组（数组中包含对象 ）</span></span><br><span class="line"><span class="keyword">const</span> obj3 = [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, &#123; <span class="attr">a</span>: <span class="string">&#x27;a&#x27;</span> &#125;, &#123; <span class="attr">b</span>: <span class="string">&#x27;b&#x27;</span> &#125;, &#123; <span class="attr">c</span>: <span class="string">&#x27;c&#x27;</span> &#125;];</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">entries</span>(obj3));</span><br><span class="line"></span><br><span class="line"><span class="comment">// 参数为数组（数组中元素为对象）</span></span><br><span class="line"><span class="keyword">const</span> obj4 = [&#123; <span class="attr">a</span>: <span class="string">&#x27;a&#x27;</span> &#125;, &#123; <span class="attr">b</span>: <span class="string">&#x27;b&#x27;</span> &#125;, &#123; <span class="attr">c</span>: <span class="string">&#x27;c&#x27;</span> &#125;];</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">entries</span>(obj4));</span><br><span class="line"></span><br><span class="line"><span class="comment">// Object转换为Map</span></span><br><span class="line"><span class="comment">// new Map()构造函数接受一个可迭代的entries。借助Object.entries方法你可以很容易的将Object转换为Map。</span></span><br><span class="line"><span class="keyword">const</span> obj5 = &#123; <span class="attr">name</span>: <span class="string">&#x27;xiaoming&#x27;</span>, <span class="attr">age</span>: <span class="string">&#x27;seven&#x27;</span>, <span class="attr">sex</span>: <span class="string">&#x27;man&#x27;</span>, <span class="attr">grade</span>: <span class="string">&#x27;four&#x27;</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">entries</span>(obj5));</span><br><span class="line"><span class="keyword">const</span> map = <span class="keyword">new</span> <span class="title class_">Map</span>(<span class="title class_">Object</span>.<span class="title function_">entries</span>(obj5));</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(map);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 总结</span></span><br><span class="line"><span class="comment">// Object.entries() 可以把一个对象的键值以数组的形式遍历出来，</span></span><br><span class="line"><span class="comment">// 结果和 for...in 循环遍历该对象时返回的结果一样，但是不会遍历其原型属性。</span></span><br></pre></td></tr></table></figure>

<h2 id="Object-freeze"><a href="#Object-freeze" class="headerlink" title="Object.freeze()"></a>Object.freeze()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 我们都知道const定义基本数据类型，这个值是不可以修改的。那么我们用const定义对象，可以修改对象吗？</span></span><br><span class="line"><span class="comment">// 答案是肯定的。那么如果我们想定义一个不可被修改的对象，应该怎么办呢！那就要用到Object.freeze()了。</span></span><br><span class="line"><span class="comment">// 它的作用是冻结一个对象，被冻结的对象有以下几个特性：</span></span><br><span class="line"><span class="comment">// 1、不能添加新属性</span></span><br><span class="line"><span class="comment">// 2、不能删除已有属性</span></span><br><span class="line"><span class="comment">// 3、不能修改已有属性的值</span></span><br><span class="line"><span class="comment">// 4、不能修改原型</span></span><br><span class="line"><span class="comment">// 5、不能修改已有属性的可枚举性、可配置性、可写性</span></span><br><span class="line"><span class="keyword">var</span> obj = &#123; <span class="attr">name</span>: <span class="string">&#x27;张三&#x27;</span>, <span class="attr">age</span>: <span class="number">18</span>, <span class="attr">address</span>: <span class="string">&#x27;上海市&#x27;</span> &#125;;</span><br><span class="line">obj.<span class="property">__proto__</span>.<span class="property">habit</span> = <span class="string">&#x27;运动&#x27;</span>;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 冻结对象</span></span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">freeze</span>(obj);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 不能添加新属性</span></span><br><span class="line">obj.<span class="property">sex</span> = <span class="string">&#x27;男&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj); <span class="comment">// &#123;name: &quot;张三&quot;, age: 18, address: &quot;上海市&quot;&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 不能删除原有属性</span></span><br><span class="line"><span class="keyword">delete</span> obj.<span class="property">age</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj); <span class="comment">// &#123;name: &quot;张三&quot;, age: 18, address: &quot;上海市&quot;&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 不能修改已有属性的值</span></span><br><span class="line">obj.<span class="property">name</span> = <span class="string">&#x27;李四&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj); <span class="comment">// &#123;name: &quot;张三&quot;, age: 18, address: &quot;上海市&quot;&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 不能修改原型</span></span><br><span class="line">obj.<span class="property">__proto__</span> = <span class="string">&#x27;随便什么值&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj.<span class="property">__proto__</span>); <span class="comment">// &#123;habit: &quot;运动&quot;, constructor: ƒ, __defineGetter__: ƒ, __defineSetter__: ƒ, hasOwnProperty: ƒ, …&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 不能修改已有属性的可枚举性、可配置性、可写性</span></span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(obj, <span class="string">&#x27;address&#x27;</span>, &#123;</span><br><span class="line">  <span class="comment">// TypeError: Cannot redefine property: address</span></span><br><span class="line">  <span class="attr">enumerable</span>: <span class="literal">false</span>,</span><br><span class="line">  <span class="attr">configurable</span>: <span class="literal">false</span>,</span><br><span class="line">  <span class="attr">writable</span>: <span class="literal">true</span></span><br><span class="line">&#125;);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 这里要注意一点，Object.freeze()的返回值就是被冻结的对象，该对象完全等于传入的对象，</span></span><br><span class="line"><span class="comment">// 所以我们一般不需要接收返回值。上面我们对对象进行了冻结，那么我们可以冻结数组吗？</span></span><br><span class="line"><span class="comment">// 冻结数组</span></span><br><span class="line"><span class="keyword">var</span> arr = [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>];</span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">freeze</span>(arr);</span><br><span class="line">arr[<span class="number">0</span>] = <span class="string">&#x27;新值&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(arr); <span class="comment">// [1, 2, 3, 4, 5]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 其实很容易能想明白，数组本质也就是对象，只不过对象的key是下标，</span></span><br><span class="line"><span class="comment">// 所以也可以冻结。如果我的对象里还有对象呢，那么冻结是否依然有效？</span></span><br><span class="line"><span class="comment">// 浅冻结</span></span><br><span class="line"><span class="keyword">var</span> obj = &#123; <span class="attr">name</span>: <span class="string">&#x27;张三&#x27;</span>, <span class="attr">info</span>: &#123; <span class="attr">a</span>: <span class="number">1</span>, <span class="attr">b</span>: <span class="number">2</span> &#125; &#125;;</span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">freeze</span>(obj);</span><br><span class="line">obj.<span class="property">name</span> = <span class="string">&#x27;李四&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj); <span class="comment">// &#123;info: &#123;a: 1, b: 2&#125;,name: &quot;张三&quot;&#125;</span></span><br><span class="line">obj.<span class="property">info</span>.<span class="property">a</span> = <span class="number">66</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj.<span class="property">info</span>); <span class="comment">// &#123;a: 66, b: 2&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 可以看到对象中如果还有对象的时候，Object.freeze()失效了。</span></span><br><span class="line"><span class="comment">// Object.freeze()只支持浅冻结，下面我们封装一个深冻结函数，日后可直接使用</span></span><br><span class="line"><span class="comment">// 深冻结</span></span><br><span class="line"><span class="keyword">var</span> obj = &#123; <span class="attr">name</span>: <span class="string">&#x27;张三&#x27;</span>, <span class="attr">info</span>: &#123; <span class="attr">a</span>: <span class="number">1</span>, <span class="attr">b</span>: <span class="number">2</span> &#125; &#125;;</span><br><span class="line"><span class="keyword">function</span> <span class="title function_">deepFreeze</span>(<span class="params">obj</span>) &#123;</span><br><span class="line">  <span class="comment">// 获取所有属性</span></span><br><span class="line">  <span class="keyword">var</span> propNames = <span class="title class_">Object</span>.<span class="title function_">getOwnPropertyNames</span>(obj);</span><br><span class="line"></span><br><span class="line">  <span class="comment">// 遍历</span></span><br><span class="line">  propNames.<span class="title function_">forEach</span>(<span class="function"><span class="params">item</span> =&gt;</span> &#123;</span><br><span class="line">    <span class="keyword">var</span> prop = obj[item];</span><br><span class="line">    <span class="comment">// 如果某个属性的属性值是对象，则递归调用</span></span><br><span class="line">    <span class="keyword">if</span> (prop <span class="keyword">instanceof</span> <span class="title class_">Object</span> &amp;&amp; prop !== <span class="literal">null</span>) &#123;</span><br><span class="line">      <span class="title function_">deepFreeze</span>(prop);</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;);</span><br><span class="line">  <span class="comment">// 冻结自身</span></span><br><span class="line">  <span class="keyword">return</span> <span class="title class_">Object</span>.<span class="title function_">freeze</span>(obj);</span><br><span class="line">&#125;</span><br><span class="line"><span class="title function_">deepFreeze</span>(obj);</span><br><span class="line">obj.<span class="property">name</span> = <span class="string">&#x27;李四&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj); <span class="comment">// &#123;name: &quot;张三&quot;, info: &#123;…&#125;&#125;</span></span><br><span class="line">obj.<span class="property">info</span>.<span class="property">a</span> = <span class="number">100</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj.<span class="property">info</span>); <span class="comment">// &#123;a: 1, b: 2&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 应用场景</span></span><br><span class="line"><span class="comment">// Object.freeze()可以提高性能，如果你有一个对象，里面的内容特别特别多，</span></span><br><span class="line"><span class="comment">// 而且都是一些静态数据，你确保不会修改它们，那你其实可以用Object.freeze()冻结起来，</span></span><br><span class="line"><span class="comment">// 这样可以让性能大幅度提升，提升的效果随着数据量的递增而递增。一般什么时候用呢？</span></span><br><span class="line"><span class="comment">// 对于纯展示的大数据，都可以使用Object.freeze提升性能。</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Vue中使用Object.freeze</span></span><br><span class="line"><span class="comment">// 在vue项目中, data初始化 里面一般会有很多变量, 后续如果不想使用它, 可以使用Object.freeze()。</span></span><br><span class="line"><span class="comment">// 这样可以避免vue初始化时候, 做一些无用的操作, 从而提高性能</span></span><br><span class="line"><span class="comment">// data()&#123;</span></span><br><span class="line"><span class="comment">// return &#123;</span></span><br><span class="line"><span class="comment">// list: Object.freeze(&#123; &#x27;我不需要改变&#x27;&#125;)</span></span><br><span class="line"><span class="comment">// &#125;</span></span><br><span class="line"><span class="comment">// &#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Object.freeze()原理</span></span><br><span class="line"><span class="comment">// 模拟Object.freeze()原理主要用到两个关键方法，Object.definedProperty()、Object.seal()。</span></span><br><span class="line"><span class="comment">// Object.definedProperty()方法可以定义对象的属性的特性。如可不可以删除、可不可以修改等等</span></span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(person, <span class="string">&#x27;name&#x27;</span>, &#123;</span><br><span class="line">  <span class="attr">configurable</span>: <span class="literal">false</span>, <span class="comment">// 表示能否通过delete删除属性，能否修改属性的特性...</span></span><br><span class="line">  <span class="attr">enumerable</span>: <span class="literal">false</span>, <span class="comment">// 表示是否可以枚举。直接在对象上定义的属性，基本默认true</span></span><br><span class="line">  <span class="attr">writable</span>: <span class="literal">false</span>, <span class="comment">// 表示能否修改属性的值。直接在对象上定义的属性，基本默认true</span></span><br><span class="line">  <span class="attr">value</span>: <span class="string">&#x27;xm&#x27;</span> <span class="comment">// 表示属性的值。访问属性时从这里读取，修改属性时，也保存在这里。</span></span><br><span class="line">&#125;);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 通过上述配置，就能实现不能修改已有属性的值、不能修改已有属性的可枚举性、可配置性、可写性等等功能了</span></span><br><span class="line"><span class="comment">// Object.seal()方法可以让对象不能被扩展、删除属性等等。用法：Object.seal(person)</span></span><br><span class="line"><span class="comment">// 通过Object.seal()方法可以实现不能删除，不能新增对象属性等等功能。通过这两个方法就可以实现一个简单的freeze方法了</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">myFreeze</span>(<span class="params">obj</span>) &#123;</span><br><span class="line">  <span class="keyword">if</span> (obj <span class="keyword">instanceof</span> <span class="title class_">Object</span>) &#123;</span><br><span class="line">    <span class="title class_">Object</span>.<span class="title function_">seal</span>(obj);</span><br><span class="line">    <span class="keyword">let</span> p;</span><br><span class="line">    <span class="keyword">for</span> (p <span class="keyword">in</span> obj) &#123;</span><br><span class="line">      <span class="keyword">if</span> (obj.<span class="title function_">hasOwnProperty</span>(p)) &#123;</span><br><span class="line">        <span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(obj, p, &#123; <span class="attr">writable</span>: <span class="literal">false</span> &#125;);</span><br><span class="line">        <span class="title function_">myFreeze</span>(obj[p]);</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br></pre></td></tr></table></figure>
<h2 id="Object-keys-Object-values"><a href="#Object-keys-Object-values" class="headerlink" title="Object.keys() Object.values()"></a>Object.keys() Object.values()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.keys(obj)</span></span><br><span class="line"><span class="comment">// 参数：要返回其枚举自身属性的对象</span></span><br><span class="line"><span class="comment">// 返回值：一个表示给定对象的所有枚举属性的字符串数组</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 1、处理对象，返回可枚举的属性数组</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">keys</span>(&#123; <span class="attr">one</span>: <span class="number">1</span>, <span class="attr">two</span>: <span class="number">2</span>, <span class="attr">three</span>: <span class="number">3</span> &#125;)); <span class="comment">// [&#x27;one&#x27;, &#x27;two&#x27;, &#x27;three&#x27;]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 2、处理数组，返回索引值数组</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">keys</span>([<span class="string">&#x27;one&#x27;</span>, <span class="string">&#x27;two&#x27;</span>, <span class="string">&#x27;three&#x27;</span>])); <span class="comment">// [&#x27;0&#x27;, &#x27;1&#x27;, &#x27;2&#x27;]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 3、处理字符串，返回索引值数组</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">keys</span>(<span class="string">&#x27;one&#x27;</span>)); <span class="comment">// [&#x27;0&#x27;, &#x27;1&#x27;, &#x27;2&#x27;]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Object.values方法返回存储指定对象所有自有可枚举属性值的数组</span></span><br><span class="line"><span class="comment">// for in可以遍历原型链上的属性，Object.values不可以</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">values</span>(&#123; <span class="attr">one</span>: <span class="number">1</span>, <span class="attr">two</span>: <span class="number">2</span>, <span class="attr">three</span>: <span class="number">3</span> &#125;)); <span class="comment">// [1, 2, 3]</span></span><br><span class="line"></span><br></pre></td></tr></table></figure>

<h2 id="Object-assign"><a href="#Object-assign" class="headerlink" title="Object.assign()"></a>Object.assign()</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.assign() 方法用于将所有可枚举属性的值从一个或多个源对象复制到目标对象。它将返回目标对象。</span></span><br><span class="line"><span class="comment">// 简单来说，就是Object.assign()是对象的静态方法，</span></span><br><span class="line"><span class="comment">// 可以用来复制对象的可枚举属性到目标对象，利用这个特性可以实现对象属性的合并。</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Object.assign(target, ...sources)</span></span><br><span class="line"><span class="comment">// 参数： target-- - &gt; 目标对象</span></span><br><span class="line"><span class="comment">// source-- -&gt; 源对象</span></span><br><span class="line"><span class="comment">// 返回值：target，即目标对象</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 1、目标对象和源对象无重名属性</span></span><br><span class="line"><span class="keyword">var</span> target = &#123; <span class="attr">name</span>: <span class="string">&#x27;guxin&#x27;</span>, <span class="attr">age</span>: <span class="number">25</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> source = &#123; <span class="attr">state</span>: <span class="string">&#x27;single&#x27;</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> result = <span class="title class_">Object</span>.<span class="title function_">assign</span>(target, source);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(target, target == result);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 我们可以看到source上的state属性合并到了target对象上。</span></span><br><span class="line"><span class="comment">// 如果只是想将两个或多个对象的属性合并到一起，不改变原有对象的属性，</span></span><br><span class="line"><span class="comment">// 可以用一个空的对象作为target对象。像下面这样：</span></span><br><span class="line"><span class="keyword">var</span> result1 = <span class="title class_">Object</span>.<span class="title function_">assign</span>(&#123;&#125;, target, source);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 2、目标对象和源对象有重名属性，后面的属性值会覆盖前面的属性值。</span></span><br><span class="line"><span class="keyword">var</span> target2 = &#123; <span class="attr">name</span>: <span class="string">&#x27;guxin&#x27;</span>, <span class="attr">age</span>: <span class="number">18</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> source2 = &#123; <span class="attr">state</span>: <span class="string">&#x27;signle&#x27;</span>, <span class="attr">age</span>: <span class="number">22</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> result2 = <span class="title class_">Object</span>.<span class="title function_">assign</span>(target2, source2);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(target2);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 3、有多个源对象</span></span><br><span class="line"><span class="comment">// 没有同名的属性会直接复制到目标对象上，同名的属性后面的属性值会覆盖前面的同名属性值。</span></span><br><span class="line"><span class="keyword">var</span> target3 = &#123; <span class="attr">name</span>: <span class="string">&#x27;guxin&#x27;</span>, <span class="attr">age</span>: <span class="number">18</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> source3 = &#123; <span class="attr">state</span>: <span class="string">&#x27;signle&#x27;</span>, <span class="attr">age</span>: <span class="number">22</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> source4 = &#123; <span class="attr">mood</span>: <span class="string">&#x27;happy&#x27;</span>, <span class="attr">age</span>: <span class="number">25</span> &#125;;</span><br><span class="line"><span class="keyword">var</span> result = <span class="title class_">Object</span>.<span class="title function_">assign</span>(target3, source3, source4);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(target3);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 注意事项：</span></span><br><span class="line"><span class="comment">// 1、Object.assign 方法只会拷贝源对象自身的并且可枚举的属性到目标对象，继承属性和不可枚举属性是不能拷贝的。</span></span><br><span class="line"><span class="comment">// 2、针对深拷贝，需要使用其他办法，因为 Object.assign()拷贝的是属性值。</span></span><br><span class="line"><span class="comment">// 假如源对象的属性值是一个对象的引用，那么它也只指向那个引用。</span></span><br><span class="line"><span class="comment">// 3、目标对象自身也会改变</span></span><br><span class="line"><span class="comment">// 4、异常会打断后续拷贝任务</span></span><br><span class="line"></span><br></pre></td></tr></table></figure>
<h2 id="Object-defineProperty方法是Vue双向绑定原理的常见面试题"><a href="#Object-defineProperty方法是Vue双向绑定原理的常见面试题" class="headerlink" title="Object.defineProperty方法是Vue双向绑定原理的常见面试题"></a>Object.defineProperty方法是Vue双向绑定原理的常见面试题</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// Object.defineProperty方法是Vue双向绑定原理的常见面试题</span></span><br><span class="line"><span class="comment">// Object.defineProperty(obj, prop, descriptor) 定义新属性或者修改原有的属性</span></span><br><span class="line"><span class="comment">// obj：必需，目标对象；</span></span><br><span class="line"><span class="comment">// prop：必需，定义或修改的属性的名字；</span></span><br><span class="line"><span class="comment">// descriptor：必需，目标属性所拥有的特性</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 第三个参数descriptor说明：以对象形式&#123;&#125;书写</span></span><br><span class="line"><span class="comment">// 1、value：设置属性的值，默认为undefined</span></span><br><span class="line"><span class="comment">// 2、writable：值是否可以重写，true | false，默认为false</span></span><br><span class="line"><span class="comment">// 3、enumerable：目标属性是否可以被枚举（表示能否通过for in循环访问属性），默认为false</span></span><br><span class="line"><span class="comment">// 4、configurable：表示能否通过delete删除属性从而重新定义属性，能否修改属性的特性，</span></span><br><span class="line"><span class="comment">// 或者能否把属性修改为访问器属性，默认值为false。</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> p1 = &#123; <span class="attr">name</span>: <span class="string">&#x27;lisi&#x27;</span> &#125;;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 当configurable: false时，delete就不能把name属性给删除掉了</span></span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(p1, <span class="string">&#x27;name&#x27;</span>, &#123; <span class="attr">configurable</span>: <span class="literal">false</span> &#125;);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(p1); <span class="comment">// &#123; name: &#x27;lisi&#x27; &#125;</span></span><br><span class="line"><span class="keyword">delete</span> p1.<span class="property">name</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(p1); <span class="comment">// &#123; name: &#x27;lisi&#x27; &#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 当writable: false时，我们就无法修改这个age属性</span></span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(p1, <span class="string">&#x27;age&#x27;</span>, &#123;</span><br><span class="line">  <span class="attr">writable</span>: <span class="literal">false</span>,</span><br><span class="line">  <span class="attr">enumerable</span>: <span class="literal">true</span>,</span><br><span class="line">  <span class="attr">value</span>: <span class="number">15</span></span><br><span class="line">&#125;);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(p1.<span class="property">age</span>); <span class="comment">// 15</span></span><br><span class="line">p1.<span class="property">age</span> = <span class="number">20</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(p1.<span class="property">age</span>); <span class="comment">// 15</span></span><br><span class="line"><span class="keyword">for</span> (<span class="keyword">var</span> i <span class="keyword">in</span> p1) &#123;</span><br><span class="line">  <span class="variable language_">console</span>.<span class="title function_">log</span>(p1[i], <span class="string">&#x27;age enumerable: true&#x27;</span>);</span><br><span class="line">&#125; <span class="comment">// lisi 15</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 当enumerable: false时，这样对象就不能通过迭代器遍历出age这个属性的值了</span></span><br><span class="line"><span class="comment">// Object.defineProperty(p1, &quot;age&quot;, &#123;</span></span><br><span class="line"><span class="comment">// enumerable: false</span></span><br><span class="line"><span class="comment">// &#125;)</span></span><br><span class="line"><span class="comment">// for (var i in p1) &#123;</span></span><br><span class="line"><span class="comment">// console.log(p1[i], &#x27;age enumerable: false&#x27;);</span></span><br><span class="line"><span class="comment">// &#125; // lisi</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 另外，该方法的第三个参数除了可以是数据属性，也可以是访问器属性</span></span><br><span class="line"><span class="comment">// 1、get：在读取属性时调用的函数，默认值是undefined</span></span><br><span class="line"><span class="comment">// 2、set：在写入属性的时候调用的函数，默认值是undefined</span></span><br><span class="line"><span class="keyword">var</span> book = &#123; <span class="attr">changedYear</span>: <span class="number">2004</span>, <span class="attr">edition</span>: <span class="number">1</span> &#125;;</span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(book, <span class="string">&#x27;year&#x27;</span>, &#123;</span><br><span class="line">  <span class="title function_">get</span>(<span class="params"></span>) &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="variable language_">this</span>.<span class="property">changedYear</span>;</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="title function_">set</span>(<span class="params">newYear</span>) &#123;</span><br><span class="line">    <span class="keyword">if</span> (newYear &gt; <span class="number">2004</span>) &#123;</span><br><span class="line">      <span class="variable language_">this</span>.<span class="property">changedYear</span> = newYear;</span><br><span class="line">      <span class="variable language_">this</span>.<span class="property">edition</span> += newYear - <span class="number">2004</span>;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;);</span><br><span class="line"><span class="comment">// 由于get方法返回changedYear的值，set方法通过计算来确定正确的版本</span></span><br><span class="line"><span class="comment">// 因此把year的值设置为2005会导致edition的值变为2</span></span><br><span class="line">book.<span class="property">year</span> = <span class="number">2006</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(book.<span class="property">edition</span>); <span class="comment">// 2</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(book.<span class="property">changedYear</span>); <span class="comment">// 2005</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 定义多个属性</span></span><br><span class="line"><span class="keyword">var</span> student = &#123;&#125;;</span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperties</span>(student, &#123;</span><br><span class="line">  <span class="attr">name</span>: &#123;</span><br><span class="line">    <span class="attr">writable</span>: <span class="literal">false</span>,</span><br><span class="line">    <span class="attr">value</span>: <span class="string">&#x27;lisi&#x27;</span></span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="attr">age</span>: &#123;</span><br><span class="line">    <span class="attr">writable</span>: <span class="literal">true</span>,</span><br><span class="line">    <span class="attr">value</span>: <span class="number">16</span></span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="attr">sex</span>: &#123;</span><br><span class="line">    <span class="title function_">get</span>(<span class="params"></span>) &#123;</span><br><span class="line">      <span class="keyword">return</span> <span class="string">&#x27;男&#x27;</span>;</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="title function_">set</span>(<span class="params">v</span>) &#123;</span><br><span class="line">      p1.<span class="property">sex</span> = v;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;);</span><br><span class="line">p1.<span class="property">sex</span> = <span class="string">&#x27;男&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(student.<span class="property">name</span> + <span class="string">&#x27;:&#x27;</span> + student.<span class="property">age</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(p1.<span class="property">sex</span>); <span class="comment">// 男</span></span><br><span class="line">student.<span class="property">sex</span> = <span class="string">&#x27;女&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(student.<span class="property">sex</span>); <span class="comment">// 男</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(p1.<span class="property">sex</span>); <span class="comment">// 女</span></span><br><span class="line"><span class="comment">// 模拟Vue中v-model数据双向绑定原理</span></span><br><span class="line"><span class="keyword">let</span> text;</span><br><span class="line"><span class="variable language_">window</span>.<span class="property">data</span> = &#123;&#125;;</span><br><span class="line"><span class="keyword">const</span> input1 = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">&#x27;input1&#x27;</span>);</span><br><span class="line"><span class="keyword">const</span> input2 = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">&#x27;input2&#x27;</span>);</span><br><span class="line"><span class="keyword">function</span> <span class="title function_">inputValue</span>(<span class="params">ref</span>) &#123;</span><br><span class="line">  ref.<span class="title function_">addEventListener</span>(<span class="string">&#x27;input&#x27;</span>, <span class="keyword">function</span> (<span class="params">e</span>) &#123;</span><br><span class="line">    text = e.<span class="property">target</span>.<span class="property">value</span>;</span><br><span class="line">    <span class="variable language_">window</span>.<span class="property">data</span>.<span class="property">value</span> = text;</span><br><span class="line">  &#125;);</span><br><span class="line">&#125;</span><br><span class="line"><span class="title function_">inputValue</span>(input1);</span><br><span class="line"><span class="title function_">inputValue</span>(input2);</span><br><span class="line"><span class="title class_">Object</span>.<span class="title function_">defineProperty</span>(<span class="variable language_">window</span>.<span class="property">data</span>, <span class="string">&#x27;value&#x27;</span>, &#123;</span><br><span class="line">  <span class="title function_">get</span>(<span class="params"></span>) &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="string">&#x27;&#x27;</span>;</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="title function_">set</span>(<span class="params">v</span>) &#123;</span><br><span class="line">    input1.<span class="property">value</span> = v;</span><br><span class="line">    input2.<span class="property">value</span> = v;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;);</span><br></pre></td></tr></table></figure>

<h2 id="判断一个对象为空对象的几种方法"><a href="#判断一个对象为空对象的几种方法" class="headerlink" title="判断一个对象为空对象的几种方法"></a>判断一个对象为空对象的几种方法</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 判断一个对象为空对象的几种方法</span></span><br><span class="line"><span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 1、将对象转换为字符串，再判断是否等于&#123;&#125;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">JSON</span>.<span class="title function_">stringify</span>(obj) === <span class="string">&#x27;&#123;&#125;&#x27;</span>);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 2、for in 循环</span></span><br><span class="line"><span class="keyword">let</span> result = <span class="keyword">function</span> (<span class="params">obj</span>) &#123;</span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> key <span class="keyword">in</span> obj) &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">false</span>; <span class="comment">// 若不为空，可遍历，返回false</span></span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">result</span>(obj));</span><br><span class="line"></span><br><span class="line"><span class="comment">// 3、Object.keys()方法，返回对象的属性名组成的一个数组，</span></span><br><span class="line"><span class="comment">// 若长度为0，则为空对象（ES6的写法）</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">keys</span>(obj).<span class="property">length</span> == <span class="number">0</span>);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 4、Object.getOwnPropertyNames()方法获取对象的属性名，存到数组中，若长度为0，则为空对象</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="title function_">getOwnPropertyNames</span>(obj).<span class="property">length</span> == <span class="number">0</span>);</span><br></pre></td></tr></table></figure>

<h2 id="hasOwnProperty方法-in方法-instanceof方法"><a href="#hasOwnProperty方法-in方法-instanceof方法" class="headerlink" title="hasOwnProperty方法 in方法 instanceof方法"></a>hasOwnProperty方法 in方法 instanceof方法</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br><span class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br><span class="line">157</span><br><span class="line">158</span><br><span class="line">159</span><br><span class="line">160</span><br><span class="line">161</span><br><span class="line">162</span><br><span class="line">163</span><br><span class="line">164</span><br><span class="line">165</span><br><span class="line">166</span><br><span class="line">167</span><br><span class="line">168</span><br><span class="line">169</span><br><span class="line">170</span><br><span class="line">171</span><br><span class="line">172</span><br><span class="line">173</span><br><span class="line">174</span><br><span class="line">175</span><br><span class="line">176</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 简而言之：hasOwnProperty表示是否有自己的属性。这个方法会查找一个对象是否有某个属性，但是不会去查找它的原型链。</span></span><br><span class="line"><span class="comment">// hasOwnProperty()方法是Object的原型方法（也称为实例方法），它定义在Object.prototype对象之上，</span></span><br><span class="line"><span class="comment">// 所有Object的实例对象都会继承hasOwnProperty()方法， 返回true或false；</span></span><br><span class="line"><span class="comment">// hasOwnProperty() 只会检查对象的自有属性，对象原型上的属性其不会检测；但是对于原型对象本身来说，</span></span><br><span class="line"><span class="comment">// 这些原型上的属性又是原型对象的自有属性，所以原形对象也可以使用hasOwnProperty()检测自己的自有属性；</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">let</span> obj = &#123;</span><br><span class="line">  <span class="attr">name</span>: <span class="string">&#x27;张三&#x27;</span>,</span><br><span class="line">  <span class="attr">age</span>: <span class="number">18</span>,</span><br><span class="line">  <span class="attr">eat</span>: &#123;</span><br><span class="line">    <span class="attr">eatname</span>: <span class="string">&#x27;面条&#x27;</span>,</span><br><span class="line">    <span class="attr">water</span>: &#123;</span><br><span class="line">      <span class="attr">watername</span>: <span class="string">&#x27;农夫山泉&#x27;</span></span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  obj.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;name&#x27;</span>),</span><br><span class="line">  obj.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;age&#x27;</span>),</span><br><span class="line">  obj.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;eat&#x27;</span>)</span><br><span class="line">); <span class="comment">// 3true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  obj.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;eatname&#x27;</span>),</span><br><span class="line">  obj.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;water&#x27;</span>),</span><br><span class="line">  obj.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;watername&#x27;</span>)</span><br><span class="line">); <span class="comment">// 3false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj.<span class="property">eat</span>.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;eatname&#x27;</span>), obj.<span class="property">eat</span>.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;water&#x27;</span>)); <span class="comment">// 2true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj.<span class="property">eat</span>.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;watername&#x27;</span>)); <span class="comment">// false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(obj.<span class="property">eat</span>.<span class="property">water</span>.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;watername&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> str = <span class="keyword">new</span> <span class="title class_">String</span>();</span><br><span class="line"><span class="comment">// split方法是String这个对象的方法，str对象本身是没有这个split这个属性的</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(str.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;split&#x27;</span>)); <span class="comment">// false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">String</span>.<span class="property"><span class="keyword">prototype</span></span>.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;split&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 判断自身属性与继承属性</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">foo</span>(<span class="params"></span>) &#123;</span><br><span class="line">  <span class="variable language_">this</span>.<span class="property">name</span> = <span class="string">&#x27;foo&#x27;</span>;</span><br><span class="line">  <span class="variable language_">this</span>.<span class="property">sayHi</span> = <span class="keyword">function</span> (<span class="params"></span>) &#123;</span><br><span class="line">    <span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;Say Hi&#x27;</span>);</span><br><span class="line">  &#125;;</span><br><span class="line">&#125;</span><br><span class="line">foo.<span class="property"><span class="keyword">prototype</span></span>.<span class="property">sayGoodBy</span> = <span class="keyword">function</span> (<span class="params"></span>) &#123;</span><br><span class="line">  <span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;Say Good By&#x27;</span>);</span><br><span class="line">&#125;;</span><br><span class="line"><span class="keyword">let</span> myPro = <span class="keyword">new</span> <span class="title function_">foo</span>();</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(myPro.<span class="property">name</span>); <span class="comment">// foo</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(myPro.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;name&#x27;</span>), myPro.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;sayHi&#x27;</span>)); <span class="comment">// 2true</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  myPro.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;toString&#x27;</span>),</span><br><span class="line">  myPro.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;hasOwnProperty&#x27;</span>)</span><br><span class="line">); <span class="comment">// 2false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(myPro.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;sayGoodBy&#x27;</span>)); <span class="comment">// false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;sayGoodBy&#x27;</span> <span class="keyword">in</span> myPro); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 遍历一个对象的所有自身属性</span></span><br><span class="line"><span class="comment">// 在看开源项目的过程中，经常会看到类似如下的源码。</span></span><br><span class="line"><span class="comment">// for...in循环对象的所有枚举属性，然后再使用hasOwnProperty()方法来忽略继承属性。</span></span><br><span class="line"><span class="keyword">var</span> buz = &#123;</span><br><span class="line">  <span class="attr">fog</span>: <span class="string">&#x27;stack&#x27;</span>,</span><br><span class="line">  <span class="attr">exp</span>: <span class="string">&#x27;expect&#x27;</span></span><br><span class="line">&#125;;</span><br><span class="line"><span class="keyword">for</span> (<span class="keyword">var</span> name <span class="keyword">in</span> buz) &#123;</span><br><span class="line">  <span class="keyword">if</span> (buz.<span class="title function_">hasOwnProperty</span>(name)) &#123;</span><br><span class="line">    <span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;this is fog (&#x27;</span> + name + <span class="string">&#x27;) for sure. Value: &#x27;</span> + buz[name]);</span><br><span class="line">  &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">    <span class="variable language_">console</span>.<span class="title function_">log</span>(name); <span class="comment">// toString or something else</span></span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="comment">// 注意 hasOwnProperty 作为属性名</span></span><br><span class="line"><span class="comment">// JavaScript 并没有保护 hasOwnProperty 属性名，因此，可能存在于一个包含此属性名的对象，</span></span><br><span class="line"><span class="comment">// 有必要使用一个可扩展的hasOwnProperty方法来获取正确的结果：</span></span><br><span class="line"><span class="keyword">var</span> foo = &#123;</span><br><span class="line">  <span class="attr">hasOwnProperty</span>: <span class="keyword">function</span> (<span class="params"></span>) &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">  &#125;,</span><br><span class="line">  <span class="attr">bar</span>: <span class="string">&#x27;Here be dragons&#x27;</span></span><br><span class="line">&#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(foo.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;bar&#x27;</span>)); <span class="comment">// 始终返回 false</span></span><br><span class="line"><span class="comment">// 如果担心这种情况，可以直接使用原型链上真正的 hasOwnProperty 方法</span></span><br><span class="line"><span class="comment">// 使用另一个对象的`hasOwnProperty` 并且call</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(&#123;&#125;.<span class="property">hasOwnProperty</span>.<span class="title function_">call</span>(foo, <span class="string">&#x27;bar&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"><span class="comment">// 也可以使用 Object 原型上的 hasOwnProperty 属性</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>.<span class="property">hasOwnProperty</span>.<span class="title function_">call</span>(foo, <span class="string">&#x27;bar&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>.<span class="property">bar</span> = <span class="number">1</span>;</span><br><span class="line"><span class="keyword">var</span> fool = &#123; <span class="attr">a</span>: <span class="string">&#x27;b&#x27;</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(fool.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;bar&#x27;</span>)); <span class="comment">// false</span></span><br><span class="line">fool.<span class="property">bar</span> = <span class="number">1</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(fool.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;a&#x27;</span>), fool.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;bar&#x27;</span>)); <span class="comment">// 2true</span></span><br><span class="line"><span class="comment">// 判断自身属性是否存在</span></span><br><span class="line"><span class="keyword">var</span> o = <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">o.<span class="property">prop</span> = <span class="string">&#x27;exists&#x27;</span>;</span><br><span class="line"><span class="keyword">function</span> <span class="title function_">changeO</span>(<span class="params"></span>) &#123;</span><br><span class="line">  o.<span class="property">newprop</span> = o.<span class="property">prop</span>;</span><br><span class="line">  <span class="keyword">delete</span> o.<span class="property">prop</span>;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(o.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;prop&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"><span class="title function_">changeO</span>();</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(o.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;prop&#x27;</span>)); <span class="comment">// false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(o.<span class="title function_">hasOwnProperty</span>(<span class="string">&#x27;newprop&#x27;</span>)); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// in</span></span><br><span class="line"><span class="comment">// 如果指定的属性在指定的对象或原型链中 语法：prop in object</span></span><br><span class="line"><span class="comment">// prop：一个字符串类型或者symbol类型的属性名或数字索引（非symbol类型会被强制转换为字符串）</span></span><br><span class="line"><span class="comment">// objectName：检查它（或者原型链）是否包含具有指定名称的属性的对象</span></span><br><span class="line"><span class="comment">// in的一些用法：</span></span><br><span class="line"><span class="comment">// 数组</span></span><br><span class="line"><span class="keyword">var</span> trees = <span class="keyword">new</span> <span class="title class_">Array</span>(<span class="string">&#x27;redwood&#x27;</span>, <span class="string">&#x27;bay&#x27;</span>, <span class="string">&#x27;cedar&#x27;</span>, <span class="string">&#x27;oak&#x27;</span>, <span class="string">&#x27;maple&#x27;</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="number">0</span> <span class="keyword">in</span> trees, <span class="number">3</span> <span class="keyword">in</span> trees, <span class="number">6</span> <span class="keyword">in</span> trees); <span class="comment">// true true false</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;bay&#x27;</span> <span class="keyword">in</span> trees); <span class="comment">// false (必须使用索引号,而不是数组元素的值)</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;length&#x27;</span> <span class="keyword">in</span> trees); <span class="comment">// true (length是一个数组属性)</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Symbol</span>.<span class="property">interator</span> <span class="keyword">in</span> trees); <span class="comment">// true (数组可迭代，只在ES2015+上有效)</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 内置对象</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;PI&#x27;</span> <span class="keyword">in</span> <span class="title class_">Math</span>); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 自定义对象</span></span><br><span class="line"><span class="keyword">var</span> mycar = &#123; <span class="attr">make</span>: <span class="string">&#x27;Honda&#x27;</span>, <span class="attr">model</span>: <span class="string">&#x27;Accord&#x27;</span>, <span class="attr">year</span>: <span class="number">1998</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;make&#x27;</span> <span class="keyword">in</span> mycar, <span class="string">&#x27;model&#x27;</span> <span class="keyword">in</span> mycar); <span class="comment">// 2true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// in 右操作数必须是一个对象值，例如，你可以指定使用String构造函数创建的字符串，但不能指定字符串文字。</span></span><br><span class="line"><span class="keyword">var</span> color1 = <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&#x27;green&#x27;</span>);</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;length&#x27;</span> <span class="keyword">in</span> color1); <span class="comment">// true</span></span><br><span class="line"><span class="keyword">var</span> color2 = <span class="string">&#x27;coral&#x27;</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;length&#x27;</span> <span class="keyword">in</span> color2); <span class="comment">// 报错</span></span><br><span class="line"><span class="comment">// 如果你使用 delete 运算符删除了一个属性，则 in 运算符对所删除属性返回 false</span></span><br><span class="line"><span class="keyword">var</span> mycar = &#123; <span class="attr">make</span>: <span class="string">&#x27;Honda&#x27;</span>, <span class="attr">model</span>: <span class="string">&#x27;Accord&#x27;</span>, <span class="attr">year</span>: <span class="number">1998</span> &#125;;</span><br><span class="line"><span class="keyword">delete</span> mycar.<span class="property">make</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;make&#x27;</span> <span class="keyword">in</span> mycar); <span class="comment">// false</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 如果你只是将一个属性的值赋值为 undefined，而没有删除它，则 in 运算仍然会返回 true</span></span><br><span class="line"><span class="keyword">var</span> trees = <span class="keyword">new</span> <span class="title class_">Array</span>(<span class="string">&#x27;redwood&#x27;</span>, <span class="string">&#x27;bay&#x27;</span>, <span class="string">&#x27;cedar&#x27;</span>, <span class="string">&#x27;oak&#x27;</span>, <span class="string">&#x27;maple&#x27;</span>);</span><br><span class="line">trees[<span class="number">3</span>] = <span class="literal">undefined</span>;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="number">3</span> <span class="keyword">in</span> trees); <span class="comment">// true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 继承属性 如果一个属性是从原型链上继承来的，in 运算符也会返回 true。</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;toString&#x27;</span> <span class="keyword">in</span> &#123;&#125;); <span class="comment">// 返回true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//  instanceof 可以判断这个对象是不是某个对象的实例</span></span><br><span class="line"><span class="comment">// 用一段代码模拟instanceof内部执行过程：</span></span><br><span class="line"><span class="comment">// instanceof (A, B) = &#123;</span></span><br><span class="line"><span class="comment">// var L = A.__proto__;</span></span><br><span class="line"><span class="comment">// var R = B.prototype;</span></span><br><span class="line"><span class="comment">// if (L === R) &#123;</span></span><br><span class="line"><span class="comment">// //A的内部属性__proto__指向B的原型对象</span></span><br><span class="line"><span class="comment">// return true;</span></span><br><span class="line"><span class="comment">// &#125;</span></span><br><span class="line"><span class="comment">// return false;</span></span><br><span class="line"><span class="comment">// &#125;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(toString <span class="keyword">instanceof</span> <span class="title class_">Object</span>);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 我们发现，虽然 instanceof 能够判断出[] 是Array的实例，但它认为[] 也是Object的实例，</span></span><br><span class="line"><span class="comment">// 从 instanceof 能够判断出[].proto 指向 Array.prototype，而 Array.prototype.proto 又指向了Object.prototype，</span></span><br><span class="line"><span class="comment">// 最终 Object.prototype.proto 指向了null，标志着原型链的结束。因此，[]、Array、Object 就在内部形成了一条原型链.</span></span><br><span class="line"><span class="comment">// instanceof可以判断这个对象是不是某个对象的实例,</span></span><br><span class="line"><span class="comment">// 从原型链可以看出，[] 的 proto 直接指向Array.prototype，间接指向 Object.prototype，</span></span><br><span class="line"><span class="comment">// 所以按照 instanceof 的判断规则，[] 就是Object的实例。依次类推，类似的 new Date()、new Person() 也会形成一条对应的原型链。</span></span><br><span class="line"><span class="comment">// 因此，instanceof 只能用来判断两个对象是否属于实例关系，而不能判断一个对象实例具体属于哪种类型。</span></span><br><span class="line"><span class="comment">// 当检测Array实例时, Array.isArray 优于 instanceof, 因为Array.isArray能检测iframes.</span></span><br><span class="line"><span class="keyword">var</span> iframe = <span class="variable language_">document</span>.<span class="title function_">createElement</span>(<span class="string">&#x27;iframe&#x27;</span>);</span><br><span class="line"><span class="variable language_">document</span>.<span class="property">body</span>.<span class="title function_">appendChild</span>(iframe);</span><br><span class="line">xArray = <span class="variable language_">window</span>.<span class="property">frames</span>[<span class="variable language_">window</span>.<span class="property">frames</span>.<span class="property">length</span> - <span class="number">1</span>].<span class="property">Array</span>;</span><br><span class="line"><span class="keyword">var</span> arr = <span class="keyword">new</span> <span class="title function_">xArray</span>(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>); <span class="comment">// [1,2,3]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// Correctly checking for Array</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title class_">Array</span>.<span class="title function_">isArray</span>(arr)); <span class="comment">// true</span></span><br><span class="line"><span class="comment">// Considered harmful, because doesn&#x27;t work though iframes</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(arr <span class="keyword">instanceof</span> <span class="title class_">Array</span>); <span class="comment">// false</span></span><br><span class="line"><span class="comment">// 假如不存在 Array.isArray()，则在其他代码之前运行下面的代码将创建该方法。</span></span><br><span class="line"><span class="comment">// [] 为 [object Array], &#123;&#125; 为 [object Object]</span></span><br><span class="line"><span class="keyword">if</span> (!<span class="title class_">Array</span>.<span class="property">isArray</span>) &#123;</span><br><span class="line">  <span class="title class_">Array</span>.<span class="property">isArray</span> = <span class="keyword">function</span> (<span class="params">arg</span>) &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="title class_">Object</span>.<span class="property"><span class="keyword">prototype</span></span>.<span class="property">toString</span>.<span class="title function_">call</span>(arg) === <span class="string">&#x27;[object Array]&#x27;</span>;</span><br><span class="line">  &#125;;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="Underscore-对象部分-1-10"><a href="#Underscore-对象部分-1-10" class="headerlink" title="Underscore 对象部分 1-10"></a>Underscore 对象部分 1-10</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 1、keys_.keys(object)</span></span><br><span class="line"><span class="comment">// 检索object拥有的所有可枚举属性的名称。</span></span><br><span class="line"><span class="comment">// _.keys(&#123;one: 1, two: 2, three: 3&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; [&quot;one&quot;, &quot;two&quot;, &quot;three&quot;]</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">keys</span>(<span class="params">object</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> array = [];</span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">    array.<span class="title function_">push</span>(i);</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> array;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">keys</span>(&#123; <span class="attr">one</span>: <span class="number">1</span>, <span class="attr">two</span>: <span class="number">2</span>, <span class="attr">three</span>: <span class="number">3</span> &#125;)); <span class="comment">// [&#x27;one&#x27;, &#x27;two&#x27;, &#x27;three&#x27;]</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">keys</span>([<span class="string">&#x27;one&#x27;</span>, <span class="string">&#x27;two&#x27;</span>, <span class="string">&#x27;three&#x27;</span>])); <span class="comment">// [&#x27;0&#x27;, &#x27;1&#x27;, &#x27;2&#x27;]</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">keys</span>(<span class="string">&#x27;one&#x27;</span>)); <span class="comment">// [&#x27;0&#x27;, &#x27;1&#x27;, &#x27;2’]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 3、values_.values(object)</span></span><br><span class="line"><span class="comment">// 返回object对象所有的属性值。</span></span><br><span class="line"><span class="comment">// _.values(&#123;one: 1, two: 2, three: 3&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; [1, 2, 3]</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">values</span>(<span class="params">object</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> array = [];</span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">    array.<span class="title function_">push</span>(object[i]);</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> array;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">values</span>(&#123; <span class="attr">one</span>: <span class="number">1</span>, <span class="attr">two</span>: <span class="number">2</span>, <span class="attr">three</span>: <span class="number">3</span> &#125;)); <span class="comment">// [1, 2, 3]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 4、mapObject_.mapObject(object, iteratee, [context])</span></span><br><span class="line"><span class="comment">// 它类似于map，但是这用于对象。转换每个属性的值。</span></span><br><span class="line"><span class="comment">// _.mapObject(&#123;start: 5, end: 12&#125;, function(val, key) &#123;</span></span><br><span class="line"><span class="comment">// return val + 5;</span></span><br><span class="line"><span class="comment">// &#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;start: 10, end: 17&#125;</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">mapObject</span>(<span class="params">object, iteratee</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line">  <span class="keyword">if</span> (<span class="keyword">typeof</span> object === <span class="string">&#x27;object&#x27;</span>) &#123;</span><br><span class="line">    <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">      <span class="keyword">let</span> item = <span class="title function_">iteratee</span>(object[i], i, object);</span><br><span class="line">      obj[i] = item;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> obj;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">mapObject</span>(&#123; <span class="attr">start</span>: <span class="number">5</span>, <span class="attr">end</span>: <span class="number">12</span> &#125;, <span class="function">(<span class="params">val, key</span>) =&gt;</span> val + <span class="number">5</span>)); <span class="comment">// &#123;start: 10, end: 17&#125;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">mapObject</span>([<span class="number">5</span>, <span class="number">6</span>], <span class="function">(<span class="params">val, key</span>) =&gt;</span> val + <span class="number">5</span>)); <span class="comment">// &#123;0: 10, 1: 11&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 5、pairs_.pairs(object)</span></span><br><span class="line"><span class="comment">// 把一个对象转变为一个[key, value]形式的数组。object 逆向函数。</span></span><br><span class="line"><span class="comment">// _.pairs(&#123;one: 1, two: 2, three: 3&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; [[&quot;one&quot;, 1], [&quot;two&quot;, 2], [&quot;three&quot;, 3]]</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">paris</span>(<span class="params">object</span>) &#123;</span><br><span class="line">  <span class="keyword">if</span> (</span><br><span class="line">    <span class="keyword">typeof</span> object === <span class="string">&#x27;object&#x27;</span> &amp;&amp;</span><br><span class="line">    !<span class="title class_">Array</span>.<span class="title function_">isArray</span>(object) &amp;&amp;</span><br><span class="line">    <span class="keyword">typeof</span> object !== <span class="literal">null</span></span><br><span class="line">  ) &#123;</span><br><span class="line">    <span class="keyword">let</span> array = [];</span><br><span class="line">    <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">      array.<span class="title function_">push</span>([i, object[i]]);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> array;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">paris</span>(&#123; <span class="attr">one</span>: <span class="number">1</span>, <span class="attr">two</span>: <span class="number">2</span>, <span class="attr">three</span>: <span class="number">3</span> &#125;)); <span class="comment">// [[&quot;one&quot;, 1], [&quot;two&quot;, 2], [&quot;three&quot;, 3]]</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 6、invert_.invert(object)</span></span><br><span class="line"><span class="comment">// 返回一个object副本，使其键（keys）和值（values）对换。</span></span><br><span class="line"><span class="comment">// 对于这个操作，必须确保object里所有的值都是唯一的且可以序列号成字符串.</span></span><br><span class="line"><span class="comment">// _.invert(&#123;Moe: &quot;Moses&quot;, Larry: &quot;Louis&quot;, Curly: &quot;Jerome&quot;&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;Moses: &quot;Moe&quot;, Louis: &quot;Larry&quot;, Jerome: &quot;Curly&quot;&#125;;</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">invert</span>(<span class="params">object</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">    <span class="keyword">let</span> j = object[i];</span><br><span class="line">    obj[j] = i;</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> obj;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">invert</span>(&#123; <span class="title class_">Moe</span>: <span class="string">&#x27;Moses&#x27;</span>, <span class="title class_">Larry</span>: <span class="string">&#x27;Louis&#x27;</span>, <span class="title class_">Curly</span>: <span class="string">&#x27;Jerome&#x27;</span> &#125;));</span><br><span class="line"></span><br><span class="line"><span class="comment">// 9、findKey_.findKey(object, predicate, [context])</span></span><br><span class="line"><span class="comment">// 类似于_.findIndex ，但用于对象中的 key（键）。返回通过predicate 真值测试的 key ，</span></span><br><span class="line"><span class="comment">// 否则返回 undefined 。 predicate 通过 iteratee 进行转换，以简化速记语法。</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">findKey</span>(<span class="params">object, predicate</span>) &#123;</span><br><span class="line">  <span class="keyword">if</span> (</span><br><span class="line">    <span class="keyword">typeof</span> object === <span class="string">&#x27;object&#x27;</span> &amp;&amp;</span><br><span class="line">    !<span class="title class_">Array</span>.<span class="title function_">isArray</span>(object) &amp;&amp;</span><br><span class="line">    <span class="keyword">typeof</span> object !== <span class="literal">null</span></span><br><span class="line">  ) &#123;</span><br><span class="line">    <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">      <span class="keyword">if</span> (<span class="title function_">predicate</span>(object[i], i, object) === <span class="literal">true</span>) <span class="keyword">return</span> object[i];</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">undefined</span>;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title function_">findKey</span>(&#123; <span class="attr">a</span>: <span class="number">1</span>, <span class="attr">b</span>: <span class="number">2</span>, <span class="attr">c</span>: <span class="number">3</span>, <span class="attr">d</span>: <span class="number">4</span>, <span class="attr">e</span>: <span class="number">5</span>, <span class="attr">f</span>: <span class="number">6</span> &#125;, <span class="function"><span class="params">value</span> =&gt;</span> value &gt; <span class="number">2</span>)</span><br><span class="line">); <span class="comment">// 3</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title function_">findKey</span>(</span><br><span class="line">    &#123; <span class="attr">a</span>: <span class="number">1</span>, <span class="attr">b</span>: <span class="number">2</span>, <span class="attr">c</span>: <span class="number">3</span>, <span class="attr">d</span>: <span class="number">4</span>, <span class="attr">e</span>: <span class="number">5</span>, <span class="attr">f</span>: <span class="number">6</span> &#125;,</span><br><span class="line">    <span class="function">(<span class="params">value, key, o</span>) =&gt;</span> key === <span class="string">&#x27;f&#x27;</span></span><br><span class="line">  )</span><br><span class="line">); <span class="comment">// 6</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">findKey</span>()); <span class="comment">// undefined</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 10、extend_.extend(destination, *sources)</span></span><br><span class="line"><span class="comment">// 将source对象中的所有属性简单地覆盖到destination对象上，并且返回 destination 对象.</span></span><br><span class="line"><span class="comment">// 复制是按顺序的, 所以后面的对象属性会把前面的对象属性覆盖掉(如果有重复)。</span></span><br><span class="line"><span class="comment">// _.extend(&#123;name: &#x27;moe&#x27;&#125;, &#123;age: 50&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;name: &#x27;moe&#x27;, age: 50&#125;</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">extend</span>(<span class="params">destination</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> i = <span class="number">0</span>; i &lt; <span class="variable language_">arguments</span>.<span class="property">length</span>; i++) &#123;</span><br><span class="line">    <span class="keyword">if</span> (</span><br><span class="line">      <span class="keyword">typeof</span> <span class="variable language_">arguments</span>[i] === <span class="string">&#x27;object&#x27;</span> &amp;&amp;</span><br><span class="line">      !<span class="title class_">Array</span>.<span class="title function_">isArray</span>(<span class="variable language_">arguments</span>[i]) &amp;&amp;</span><br><span class="line">      <span class="keyword">typeof</span> <span class="variable language_">arguments</span>[i] !== <span class="literal">null</span></span><br><span class="line">    ) &#123;</span><br><span class="line">      <span class="keyword">for</span> (<span class="keyword">let</span> j <span class="keyword">in</span> <span class="variable language_">arguments</span>[i]) &#123;</span><br><span class="line">        <span class="keyword">let</span> a = j;</span><br><span class="line">        obj[a] = <span class="variable language_">arguments</span>[i][j];</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> obj;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">extend</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span> &#125;, &#123; <span class="attr">age</span>: <span class="number">50</span> &#125;, [<span class="string">&#x27;a&#x27;</span>, <span class="number">1</span>], <span class="number">4</span>, <span class="string">&#x27;yes&#x27;</span>));</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title function_">extend</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span> &#125;, &#123; <span class="attr">age</span>: <span class="number">50</span> &#125;, &#123; <span class="attr">age</span>: <span class="number">70</span> &#125;, &#123; <span class="attr">address</span>: <span class="string">&#x27;福建&#x27;</span> &#125;)</span><br><span class="line">);</span><br></pre></td></tr></table></figure>

<h2 id="Underscore-对象部分-11-20"><a href="#Underscore-对象部分-11-20" class="headerlink" title="Underscore 对象部分 11-20"></a>Underscore 对象部分 11-20</h2><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// pick_.pick(object, *keys)</span></span><br><span class="line"><span class="comment">// 返回一个object副本，只过滤出keys(有效的键组成的数组)参数指定的属性值。</span></span><br><span class="line"><span class="comment">// 或者接受一个判断函数，指定挑选哪个key。</span></span><br><span class="line"><span class="comment">// _.pick(&#123;name: &#x27;moe&#x27;, age: 50, userid: &#x27;moe1&#x27;&#125;, &#x27;name&#x27;, &#x27;age&#x27;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;name: &#x27;moe&#x27;, age: 50&#125;</span></span><br><span class="line"><span class="comment">// 12、_.pick(&#123;name: &#x27;moe&#x27;, age: 50, userid: &#x27;moe1&#x27;&#125;, function(value, key, object) &#123;</span></span><br><span class="line"><span class="comment">// return _.isNumber(value);</span></span><br><span class="line"><span class="comment">// &#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;age: 50&#125;</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">isNumber</span>(<span class="params">n</span>) &#123;</span><br><span class="line">  <span class="keyword">return</span> <span class="keyword">typeof</span> n === <span class="string">&#x27;number&#x27;</span>;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">function</span> <span class="title function_">pick</span>(<span class="params">object, keys</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line">  <span class="keyword">let</span> args = <span class="title class_">Array</span>.<span class="property"><span class="keyword">prototype</span></span>.<span class="property">slice</span>.<span class="title function_">call</span>(<span class="variable language_">arguments</span>, <span class="number">1</span>);</span><br><span class="line">  <span class="keyword">if</span> (</span><br><span class="line">    <span class="keyword">typeof</span> object === <span class="string">&#x27;object&#x27;</span> &amp;&amp;</span><br><span class="line">    !<span class="title class_">Array</span>.<span class="title function_">isArray</span>(object) &amp;&amp;</span><br><span class="line">    <span class="keyword">typeof</span> object !== <span class="literal">null</span></span><br><span class="line">  ) &#123;</span><br><span class="line">    <span class="keyword">if</span> (<span class="keyword">typeof</span> keys === <span class="string">&#x27;function&#x27;</span>) &#123;</span><br><span class="line">      <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="title function_">keys</span>(object[i], i, object) === <span class="literal">true</span>) obj[i] = object[i];</span><br><span class="line">      &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">      <span class="keyword">for</span> (<span class="keyword">let</span> i = <span class="number">0</span>; i &lt; args.<span class="property">length</span>; i++) &#123;</span><br><span class="line">        <span class="keyword">let</span> arg = args[i];</span><br><span class="line">        obj[arg] = object[arg];</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> obj;</span><br><span class="line">&#125;</span><br><span class="line"><span class="comment">// 时间复杂度o(1)、o(n^2)；空间复杂度o(1)、o(n)</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">pick</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span>, <span class="attr">age</span>: <span class="number">50</span>, <span class="attr">userid</span>: <span class="string">&#x27;moe1&#x27;</span> &#125;, <span class="string">&#x27;name&#x27;</span>, <span class="string">&#x27;age&#x27;</span>));</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title function_">pick</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span>, <span class="attr">age</span>: <span class="number">50</span>, <span class="attr">userid</span>: <span class="string">&#x27;moe1&#x27;</span> &#125;, <span class="function"><span class="params">value</span> =&gt;</span> <span class="title function_">isNumber</span>(value))</span><br><span class="line">);</span><br><span class="line"><span class="comment">// 13、omit_.omit(object, *keys)</span></span><br><span class="line"><span class="comment">// 返回一个object副本，只过滤出除去keys(有效的键组成的数组)参数指定的属性值。</span></span><br><span class="line"><span class="comment">// 或者接受一个判断函数，指定忽略哪个key。</span></span><br><span class="line"><span class="comment">// _.omit(&#123;name: &#x27;moe&#x27;, age: 50, userid: &#x27;moe1&#x27;&#125;, &#x27;userid&#x27;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;name: &#x27;moe&#x27;, age: 50&#125;</span></span><br><span class="line"><span class="comment">// _.omit(&#123;name: &#x27;moe&#x27;, age: 50, userid: &#x27;moe1&#x27;&#125;, function(value, key, object) &#123;</span></span><br><span class="line"><span class="comment">// return _.isNumber(value);</span></span><br><span class="line"><span class="comment">// &#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;name: &#x27;moe&#x27;, userid: &#x27;moe1&#x27;&#125;</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">isNumber</span>(<span class="params">n</span>) &#123;</span><br><span class="line">  <span class="keyword">return</span> <span class="keyword">typeof</span> n === <span class="string">&#x27;number&#x27;</span>;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">function</span> <span class="title function_">omit</span>(<span class="params">object, keys</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line">  <span class="keyword">let</span> args = <span class="title class_">Array</span>.<span class="property"><span class="keyword">prototype</span></span>.<span class="property">slice</span>.<span class="title function_">call</span>(<span class="variable language_">arguments</span>, <span class="number">1</span>);</span><br><span class="line">  <span class="keyword">if</span> (</span><br><span class="line">    <span class="keyword">typeof</span> object === <span class="string">&#x27;object&#x27;</span> &amp;&amp;</span><br><span class="line">    !<span class="title class_">Array</span>.<span class="title function_">isArray</span>(object) &amp;&amp;</span><br><span class="line">    <span class="keyword">typeof</span> object !== <span class="literal">null</span></span><br><span class="line">  ) &#123;</span><br><span class="line">    <span class="keyword">if</span> (<span class="keyword">typeof</span> keys === <span class="string">&#x27;function&#x27;</span>) &#123;</span><br><span class="line">      <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="title function_">keys</span>(object[i]) === <span class="literal">false</span>) obj[i] = object[i];</span><br><span class="line">      &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">      <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">        <span class="keyword">if</span> (args.<span class="title function_">indexOf</span>(i) === -<span class="number">1</span>) obj[i] = object[i];</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> obj;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">omit</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span>, <span class="attr">age</span>: <span class="number">50</span>, <span class="attr">userid</span>: <span class="string">&#x27;moe1&#x27;</span> &#125;, <span class="string">&#x27;userid&#x27;</span>)); <span class="comment">//&#123;name: &#x27;moe&#x27;, age: 50&#125;</span></span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(</span><br><span class="line">  <span class="title function_">omit</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span>, <span class="attr">age</span>: <span class="number">50</span>, <span class="attr">userid</span>: <span class="string">&#x27;moe1&#x27;</span> &#125;, <span class="function"><span class="params">value</span> =&gt;</span> <span class="title function_">isNumber</span>(value))</span><br><span class="line">); <span class="comment">//&#123;name: &#x27;moe&#x27;, userid: &#x27;moe1&#x27;&#125;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 14、defaults_.defaults(object, *defaults)</span></span><br><span class="line"><span class="comment">// 用defaults对象填充object 中的undefined属性。 并且返回这个object。</span></span><br><span class="line"><span class="comment">// 一旦这个属性被填充，再使用defaults方法将不会有任何效果。</span></span><br><span class="line"><span class="comment">// var iceCream = &#123;flavor: &quot;chocolate&quot;&#125;;</span></span><br><span class="line"><span class="comment">// _.defaults(iceCream, &#123;flavor: &quot;vanilla&quot;, sprinkles: &quot;lots&quot;&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;flavor: &quot;chocolate&quot;, sprinkles: &quot;lots&quot;&#125;</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">defaults</span>(<span class="params">object, defaul</span>) &#123;</span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> defaul) &#123;</span><br><span class="line">    <span class="keyword">if</span> (object.<span class="title function_">hasOwnProperty</span>(i)) object[i] = defaul[i];</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">return</span> object;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">const</span> iceCream = &#123; <span class="attr">flavor</span>: <span class="string">&#x27;chocolate&#x27;</span> &#125;;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">defaults</span>(iceCream, &#123; <span class="attr">flavor</span>: <span class="string">&#x27;vanilla&#x27;</span>, <span class="attr">sprinkles</span>: <span class="string">&#x27;lots&#x27;</span> &#125;)); <span class="comment">// &#123;flavor: vanilla&#125;</span></span><br><span class="line"><span class="comment">// 15、clone_.clone(object)</span></span><br><span class="line"><span class="comment">// 创建 一个浅复制（浅拷贝）的克隆object。任何嵌套的对象或数组都通过引用拷贝，不会复制。</span></span><br><span class="line"><span class="comment">// _.clone(&#123;name: &#x27;moe&#x27;&#125;);</span></span><br><span class="line"><span class="comment">// =&gt; &#123;name: &#x27;moe&#x27;&#125;;</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//浅拷贝：只拷贝一层数据；复杂数据只是拷贝地址；</span></span><br><span class="line"><span class="comment">//注意：当对象中还存在复杂数据类型的时候，只是拷贝地址引用，所以新对象对其修改值的时候，还会影响原来的对象中的值</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">clone</span>(<span class="params">object</span>) &#123;</span><br><span class="line">  <span class="keyword">let</span> obj = &#123;&#125;;</span><br><span class="line">  <span class="comment">// 方法一：使用循环遍历对象，将其键值赋值给一个新数组</span></span><br><span class="line">  <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">    obj[i] = object[i];</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="comment">// 方法二：采用Object.assign(新数组，拷贝的数组)方法</span></span><br><span class="line">  <span class="comment">// Object.assign(obj, object);</span></span><br><span class="line">  <span class="keyword">return</span> obj;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">clone</span>(&#123; <span class="attr">name</span>: <span class="string">&#x27;moe&#x27;</span>, <span class="attr">age</span>: <span class="number">18</span>, <span class="attr">sex</span>: <span class="string">&#x27;男&#x27;</span> &#125;));</span><br><span class="line"></span><br><span class="line"><span class="comment">// 17、has_.has(object, key)</span></span><br><span class="line"><span class="comment">// 对象是否包含给定的键吗？等同于object.hasOwnProperty(key)，</span></span><br><span class="line"><span class="comment">// 但是使用hasOwnProperty 函数的一个安全引用，以防意外覆盖。</span></span><br><span class="line"><span class="comment">// _.has(&#123;a: 1, b: 2, c: 3&#125;, &quot;b&quot;);</span></span><br><span class="line"><span class="comment">// =&gt; true</span></span><br><span class="line"><span class="keyword">function</span> <span class="title function_">has</span>(<span class="params">object, key</span>) &#123;</span><br><span class="line">  <span class="keyword">if</span> (<span class="keyword">typeof</span> object === <span class="string">&#x27;object&#x27;</span> &amp;&amp; !<span class="title class_">Array</span>.<span class="title function_">isArray</span>(object) &amp;&amp; object !== <span class="literal">null</span>) &#123;</span><br><span class="line">    <span class="keyword">for</span> (<span class="keyword">let</span> i <span class="keyword">in</span> object) &#123;</span><br><span class="line">      <span class="keyword">if</span> (key === i) <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">has</span>(&#123; <span class="attr">a</span>: <span class="number">1</span>, <span class="attr">b</span>: <span class="number">2</span>, <span class="attr">c</span>: <span class="number">3</span> &#125;, <span class="string">&#x27;b&#x27;</span>));</span><br><span class="line"><span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="title function_">has</span>(&#123; <span class="attr">a</span>: <span class="number">1</span>, <span class="attr">b</span>: <span class="number">2</span>, <span class="attr">c</span>: <span class="number">3</span> &#125;, <span class="string">&#x27;e&#x27;</span>));</span><br><span class="line"></span><br></pre></td></tr></table></figure>

<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"></span><br></pre></td></tr></table></figure>

<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"></span><br></pre></td></tr></table></figure>

<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"></span><br></pre></td></tr></table></figure>

<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"></span><br></pre></td></tr></table></figure>
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  }

  volantis.pjax.push(() => {
    if (!document.querySelectorAll(".swiper-container")[0]) return;
    if (typeof volantis.swiper === "undefined") {
      load_swiper();
    } else {
      pjax_swiper();
    }
  });
</script>


<!-- pjax 标签必须存在于所有页面 否则 pjax error -->
<pjax>

</pjax>

<script>
  function listennSidebarTOC() {
    const navItems = document.querySelectorAll(".toc li");
    if (!navItems.length) return;
    let targets = []
    const sections = [...navItems].map((element) => {
      const link = element.querySelector(".toc-link");
      const target = document.getElementById(
        decodeURI(link.getAttribute("href")).replace("#", "")
      );
      targets.push(target)
      // 解除 a 标签 href 的 锚点定位, a 标签 href 的 锚点定位 会随机启用?? 产生错位???
      link.setAttribute("onclick","return false;")
      link.setAttribute("toc-action","toc-"+decodeURI(link.getAttribute("href")).replace("#", ""))
      link.setAttribute("href","/")
      // 配置 点击 触发新的锚点定位
      link.addEventListener("click", (event) => {
        event.preventDefault();
        // 这里的 addTop 是通过错位使得 toc 自动展开.
        volantis.scroll.to(target,{addTop: 5, observer:true})
        // Anchor id
        history.pushState(null, document.title, "#" + target.id);
      });
      return target;
    });

    function activateNavByIndex(target) {
      if (target.classList.contains("active-current")) return;

      document.querySelectorAll(".toc .active").forEach((element) => {
        element.classList.remove("active", "active-current");
      });
      target.classList.add("active", "active-current");
      let parent = target.parentNode;
      while (!parent.matches(".toc")) {
        if (parent.matches("li")) parent.classList.add("active");
        parent = parent.parentNode;
      }
    }

    // 方案一：
    volantis.activateNavIndex=0
    activateNavByIndex(navItems[volantis.activateNavIndex])
    volantis.scroll.push(()=>{
      if (targets[0].getBoundingClientRect().top >= 0) {
        volantis.activateNavIndex = 0
      }else if (targets[targets.length-1].getBoundingClientRect().top < 0) {
        volantis.activateNavIndex = targets.length-1
      } else {
        for (let index = 0; index < targets.length; index++) {
          const target0 = targets[index];
          const target1 = targets[(index+1)%targets.length];
          if (target0.getBoundingClientRect().top < 0&&target1.getBoundingClientRect().top >= 0) {
            volantis.activateNavIndex=index
            break;
          }
        }
      }
      activateNavByIndex(navItems[volantis.activateNavIndex])
    })

    // 方案二：
    // IntersectionObserver 不是完美精确到像素级别 也不是低延时性的
    // function findIndex(entries) {
    //   let index = 0;
    //   let entry = entries[index];
    //   if (entry.boundingClientRect.top > 0) {
    //     index = sections.indexOf(entry.target);
    //     return index === 0 ? 0 : index - 1;
    //   }
    //   for (; index < entries.length; index++) {
    //     if (entries[index].boundingClientRect.top <= 0) {
    //       entry = entries[index];
    //     } else {
    //       return sections.indexOf(entry.target);
    //     }
    //   }
    //   return sections.indexOf(entry.target);
    // }
    // function createIntersectionObserver(marginTop) {
    //   marginTop = Math.floor(marginTop + 10000);
    //   let intersectionObserver = new IntersectionObserver(
    //     (entries, observe) => {
    //       let scrollHeight = document.documentElement.scrollHeight;
    //       if (scrollHeight > marginTop) {
    //         observe.disconnect();
    //         createIntersectionObserver(scrollHeight);
    //         return;
    //       }
    //       let index = findIndex(entries);
    //       activateNavByIndex(navItems[index]);
    //     }, {
    //       rootMargin: marginTop + "px 0px -100% 0px",
    //       threshold: 0,
    //     }
    //   );
    //   sections.forEach((element) => {
    //     element && intersectionObserver.observe(element);
    //   });
    // }
    // createIntersectionObserver(document.documentElement.scrollHeight);
  }

  document.addEventListener("DOMContentLoaded", ()=>{
    volantis.requestAnimationFrame(listennSidebarTOC)
  });
  document.addEventListener("pjax:success", ()=>{
    volantis.requestAnimationFrame(listennSidebarTOC)
  });
</script>



<script>
  document.onreadystatechange = function () {
    if (document.readyState == 'complete') {
      // 页面加载完毕 样式加载失败，或是当前网速慢，或是开启了省流模式
      const { saveData, effectiveType } = navigator.connection || navigator.mozConnection || navigator.webkitConnection || {}
      if (getComputedStyle(document.querySelector("#safearea"), null)["display"] == "none" || saveData || /2g/.test(effectiveType)) {
        document.querySelectorAll(".reveal").forEach(function (e) {
          e.style["opacity"] = "1";
        });
        document.querySelector("#safearea").style["display"] = "block";
      }
    }
  }
</script>


  <script type="application/ld+json">[{"@context":"http://schema.org","@type":"Organization","name":"Knowledge","url":"http://example.com/","logo":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png","width":192,"height":192}},{"@context":"http://schema.org","@type":"Person","name":"weijt","image":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png"},"url":"http://example.com/","sameAs":["https://github.com/volantis-x"],"description":"html css node vue node"},{"@context":"http://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"http://example.com/","name":"Knowledge"}},{"@type":"ListItem","position":3,"item":{"@id":"http://example.com/2023/12/19/Object/","name":"Object"}}]},{"@context":"http://schema.org","@type":"WebSite","name":"Knowledge","url":"http://example.com/","keywords":"html css node vue node","description":"html css node vue node","author":{"@type":"Person","name":"weijt","image":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png"},"url":"http://example.com/","description":"html css node vue node"},"publisher":{"@type":"Organization","name":"Knowledge","url":"http://example.com/","logo":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png","width":192,"height":192}},"potentialAction":{"@type":"SearchAction","name":"Site Search","target":{"@type":"EntryPoint","urlTemplate":"http://example.com?s={search_term_string}"},"query-input":"required name=search_term_string"}},{"@context":"http://schema.org","@type":"BlogPosting","headline":"Object","description":"html css node vue node","inLanguage":"en","mainEntityOfPage":{"@type":"WebPage","@id":"http://example.com/2023/12/19/Object/"},"author":{"@type":"Person","name":"weijt","image":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png"},"url":"http://example.com/"},"publisher":{"@type":"Organization","name":"Knowledge","logo":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png","width":192,"height":192}},"url":"http://example.com/2023/12/19/Object/","wordCount":0,"datePublished":"2023-12-19T05:40:59.902Z","dateModified":"2024-06-13T01:40:03.066Z","keywords":"Object","image":{"@type":"ImageObject","url":"https://unpkg.com/volantis-static@0.0.1654736714924/media/org.volantis/blog/favicon/android-chrome-192x192.png","width":192,"height":192}}]</script>



      
        <!--
  pjax重载区域接口：
  1.  <pjax></pjax> 标签 pjax 标签必须存在于所有页面 否则 pjax error
  2.  script[data-pjax]
  3.  .pjax-reload script
  4.  .pjax
-->



<script src="https://unpkg.com/volantis-static@0.0.1654736714924/libs/pjax/pjax.min.js"></script>


<script>
    var pjax;
    document.addEventListener('DOMContentLoaded', function () {
      pjax = new Pjax({
        elements: 'a[href]:not([href^="#"]):not([href="javascript:void(0)"]):not([pjax-fancybox]):not([onclick="return false;"]):not([onclick="return!1"]):not([target="_blank"]):not([target="view_window"]):not([href$=".xml"])',
        selectors: [
          "head title",
          "head meta[name=keywords]",
          "head meta[name=description]",
          
          "#l_main",
          "#pjax-header-nav-list",
          ".pjax",
          "pjax", // <pjax></pjax> 标签
          "script[data-pjax], .pjax-reload script" // script标签添加data-pjax 或 script标签外层添加.pjax-reload 的script代码段重载
        ],
        cacheBust: false,   // url 地址追加时间戳，用以避免浏览器缓存
        timeout: 5000,
        
      });
    });

    document.addEventListener('pjax:send', function (e) {
      //window.stop(); // 相当于点击了浏览器的停止按钮

      try {
        var currentUrl = window.location.pathname;
        var targetUrl = e.triggerElement.href;
        var banUrl = [""];
        if (banUrl[0] != "") {
          banUrl.forEach(item => {
            if(currentUrl.indexOf(item) != -1 || targetUrl.indexOf(item) != -1) {
              window.location.href = targetUrl;
            }
          });
        }
      } catch (error) {}

      // 使用 volantis.pjax.send 方法传入pjax:send回调函数 参见layout/_partial/scripts/global.ejs
      volantis.pjax.method.send.start();
    });

    document.addEventListener('pjax:complete', function () {
      // 使用 volantis.pjax.push 方法传入重载函数 参见layout/_partial/scripts/global.ejs
      volantis.pjax.method.complete.start();
    });

    document.addEventListener('pjax:error', function (e) {
      if(volantis.debug) {
        console.error(e);
        console.log('pjax error: \n' + JSON.stringify(e));
      }else{
        // 使用 volantis.pjax.error 方法传入pjax:error回调函数 参见layout/_partial/scripts/global.ejs
        volantis.pjax.method.error.start();
        window.location.href = e.triggerElement.href;
      }
    });
</script>

      
    </div>
    <!-- import body_end begin-->
    <!-- import body_end end-->
    <!-- Custom Files bodyEnd begin-->
    
    <!-- Custom Files bodyEnd end-->
    <!-- front-matter body_end begin -->
    <!-- front-matter body_end end -->
  </body>
</html>
